How can I report the agency that comes to take care of my sister? They don't come.

You don't need to report them, just terminate them and find a more reliable agency.

Just an FYI, some agencies in our state are non-medical home health agencies and are not overseen by the state. They only provide home health aides. They are not reimbursed by Medicare or Medicaid because they do not provide any medical or other reimbursable services (e.g., nursing, PT). (Services from such agencies can, however, be reimbursed by some long term care insurance policies.) If the agency you are using regularly has people not show up, and they don't make any effort to get substitutes to come, then definitely look for another agency.

These agencies probably are overseen by the State but the State can't make their employees show up. That seems to be the problem. Whoever is being assigned to your sister is not coming. Is she paying out of pocket or is Medicaid footing the bill. If Medicaid is footing the bill and the agency is billing them then that is fraud and Medicaid should be informed that sister is not receiving the care. I hope sister isn't being charged for no shows.

Have you contacted the manager of the agency to report that no one shows up? Notify your sister's PCP.
How about calling the Council on Aging.

The day my FIL DIED, his care agency came by, knocked on the door, he didn't answer so they charted it as a 'no-show' and went about their day. They didn't even CALL to see if he was OK.

When I found this out--I blew a total head gasket. They were supposed to LAY EYES on their client, not knock once or twice and leave. They knew he was a huge fall risk and minimally needed his dressings changed and his breakfast.

I filed a claim and let it go. They were terrible and I knew they were when DH and his sis hired them, but nobody ever listens to me.

You report them to every government and state agency there is who has anything to do with services for handicapped people.
This is abuse and abuse must always be reported.
APS (Adult Protective Services) in your state are the first people you should speak to. Once they get the bit between their teeth, they don't let up.
Then report the agency to the Chamber of Commerce in your state or city and then to the Better Business Bureau. Then speak to the police department. The cops will help you and direct you to other state agencies that you should be speaking to. They will also do wellness checks on your sister. If your sister's help isn't there when the cops show up to do a wellness check on her, that agency is going to get some trouble.
May I ask how your sister's services are paid for? Does she receive Medicare or Medicaid? If she does, these people are always interested when there's possible billing fraud going on. There is fraud going on and I'd be willing to bet my two front teeth the agency is billing and getting paid for those caregiving services that they aren't providing. I've worked for several care agencies before going private. The worker always has to have the paperwork signed by the client or their representative every time they show up. The paperwork is triplicate. The agency gets the original, the client gets one copy, and the worker gets the other. So, you always have a copy of the hours that were worked and billed. Medicare, Medicaid, or whatever insurance might be paying will be very interested in seeing this paperwork if you have it. If the hours don't match up to what was billed, that agency will have a problem.
Get 'em girl! Don't let these people scam, fraud, and get away with what they're pulling. I hope I have been of help to you.

Agreed--home health aide services are covered by Medicare and Medicaid, but for Medicare the agency providing the services needs to be certified. "Non-certified" agencies are perfectly fine for home health aide services--they just don't provide so-called skilled services such as nursing, PT, etc. Medicare only provides home health aide services if the client is eligible for, and receiving, other skilled services such as PT. Medicaid is slightly different, and criteria vary by state. In some states, "self-directed" Medicaid benefits are allowed, meaning the person can select their own aides; family member services are can also be paid by Medicaid.

With the issues my elderly mother encountered, if she were in a nursing home, there would have been many people that could have been held responsible. Since she was being cared for in home, not many are concerned. I'm sorry but something needs to change within the industry.