My MIL has dementia. She has constant problems with her hearing aids. Claims they don't work.They work fine. What do I do?

Your MIL's brain is broken. Of course she can't figure out how to use her hearing aides.
You could spend 5 hours with her trying to teach and show her what to do and within minutes she will forget.
You may have to accept that she won't be able to wear them, and you all will just have to talk loud.
Losing the ability to comprehend is very common with folks that have dementia, so you are going to have to pick your battles with your MIL. I'm not sure this one is worth fighting.

People who wear HAs often have problems with ear wax, has anyone checked that?

You may be right about having a processing issue. In that case, maybe you should talk to her doctor about it to find out if there’s anything to be done.

My LO’s doctor advises that he needs the best hearing aids money can buy. That’s partly because dementia is closely linked to hearing issues, and I’m sure that’s true. What doctor didn’t mention was what to do if the brain is unable to process the signals coming into it from the ears.

I’m inclined to think that if they can’t process, there’s no point in wearing hearing aids. If you find out, please post and let us know.

Thought my step-mother was getting hard of hearing took her to an audiologist, slight loss in one ear.

He recognized that she had dementia said "Don't waste your money" she won't be able to mange them, her issue is processing not hearing".

That ended that, and he was right.

We bought “top of the line, very expensive” hearing aids for Papa (with his money) - they didn’t work, the battery needed changed, etc. etc. Every day we were messing with this stupid things. He would have them torn apart when we got there, but couldn’t put the new batteries and filters in because of big clumsy fingers and Parkinson’s. Every day. The hearing tech that came to the house said those supplies were meant to last a long time and he was replacing them weekly.

We all finally just gave up. He couldn’t get it. He couldn’t hear. We were exhausted. $7000 hearing aids just sat in the box while we continued to scream at him. Lewy Body Dementia was the big disconnect. The hearing aids and all the parts were fine, his brain wasn’t.

At some point, you just may have to give up. For your own sanity.

After purchasing three pairs of hearing aids for my husband with dementia and he still complained about not being able to hear. Interestingly, he could hear sometimes and not hear other times. Finally, I gave up and quit dealing with the hearing aid issue. I told the Memory Care staff to not worry about his hearing. It saved everyone a lot of grief.

My mom has the same issues but with other electronic devices since she doesn’t need hearing aids. It’s the dementia.

Like your mom, she claims they don’t work, removes the batteries, puts them back in backwards, loses the batteries, and so on. I get them working again and before you know it she has taken it apart to “fix” it or replace the batteries.

If I ask her why she would replace brand new batteries that were working the day before as clearly that wasn’t the issue she realizes that doesn’t make sense and gets embarrassed but she also says it wasn’t working and she was trying to fix it. Then she asks for a new one or if I fix it she asks what I did. I tell her “Whatever you do don’t open it up because it will only make it worse” but it goes in one ear and out the other.

She can’t come to terms with the fact that the problem is with her and not the devices. She constantly asks for a new cell phone despite having a brand new iPhone and a new iPad as well because “this one is old and doesn’t work” even though it works fine. Same with the cable box. She takes all the wires apart and then wants a new one. Sometimes she loses the components so even I can’t help her. I tell her to call the cable company and bless them they usually fix it for her.

At some point when she kept taking things apart I stopped fixing them for her. She got mad for awhile but eventually asked nicely me to help her so I did. However, when she inevitably takes them apart I do so on my own time. I have noticed that things seem to be breaking less often as a result because she knows she will just be without until I feel like helping so she is less inclined to fiddle.

If she has used hearing aids for a while so is used to them and wants to use them which sounds like might be the case the two, three things I would look into are getting her tested for processing so you know what your dealing with, ear wax and getting rechargeable hearing aids so batteries aren’t an issue. The staff that takes them out at night can put them in the charger. I agree that you want to be careful about letting her get into a pattern off calling you for help every day so doing all of these things at once and then just saying “ they must not have gotten enough charge last night you will have to try again tomorrow” or something instead of trying to fix it in person immediately might help nip the behavior in the bud.

Yes--recent studies are saying hearing loss is a risk factor for dementia, and the brain loss with dementia affects hearing and interpretation.
My mom can hear well one day and not so well another, so I'm with you. I think she has days where it's hard for her to process.

You are correct, it is a " processing" and , I would add a retention issue, both S/ S of her " dementia" . She will not remember what you tell her as short term memory is affected by dementia. Processing, following directions, also affected by dementia.
I would confer with the audiologist or hearing aid specialist and her PCP to get a consensus on options going forward. It is only anxiety provoking to everyone to continue with the current situation; no matter how many times you explain the batteries etc, she will not remember; and, she will not remember that she has called you so she keeps calling....

Practice good self care !