Mother's husband refuses to pay bill at nursing home and informed me, her daughter, he didn't sign her up for Medicaid this year.

Whatever you do, do not sign anything the nursing may ask you to which may make you financially responsible.

Did the POA document assign a successor?

Gee,
I was just playing the devil's advocate, but you certainly know more about your stepfather's motivations than I do. Someone needs to be an advocate for your mother if she is no longer able; should be your stepfather, but it could be you, the NH (perhaps), or the State of Florida. As others have suggested, I would probably start by talking to the NH and contacting APS in Florida.
https://www.napsa-now.org/get-help/help-in-your-area/florida/

You don't have to report anything to APS just yet, but at least ask them these questions. If you wish to report suspected neglect, you can do so online at https://reportabuse.dcf.state.fl.us/Adult/AdultForm.aspx. I'm not certain about this, but I think the State of Florida requires anyone (not just nurses, doctors, etc.) who suspects neglect to report it.

if you are at all interested in what is happening to your mother, then call the nursing home to find out what happened. There is usually some sort of financial responsibility form signed on admission so who signed it? And where is her disability check going? Hopefully to facility. I don’t see how he can write off his responsibilty to her if he is a designated POA. I guess she would have to take him off as POA. It it is scary that he could be making medical decisions for her.

Gee below you stated in a reply, "He wants money from her kids."

If your mom has been on Medicaid, what money? If she is in LTC or MC, then Medicaid pays all of it.

If she's been on Medicaid, then she has no assets, hence filling out her application is just a matter of her SSN, address, birthdate, most recent bank statement, etc. There are no assets except maybe a minimum amount of $ in her bank account. I reapply for my MIL every year and the only "new" information is her most recent checking acct statement. So, FIL doesn't have to put a lot of effort into a Medicaid app, unless she is on SSDI? You need to get accurate info about what is going on, as it is not making sense.

Below you also stated that "he's done". I would make one more call to her husband and clarify that he is resigning his PoA (and I'm not sure if he needs a legal doc to do this) and if so, then you should contact the NH and let them know what is going on so they can decide to find a guardian for your mom if no one else is willing to step up to PoA. It is possible he is struggling with cognitive issues himself, which would explain the irrationality of what he did. If you have solid reason to believe her husband (your stepfather?) is teetering into cognitive issues, your mother can sign new PoA legal docs assigning someone else for this responsibility if she has no cognitive impairment herself.

DO NOT send any money. It is NOT your responsibility! You can contact APS in Florida (do so anonymously if you wish) and tell them your Mother (just give them her name and where she is now) is not being taken care of financially. They should be able to determine and follow the right path to help your Mother.

Nursing home can apply for emergency guardianship then they can take care of her paperwork. Just make sure NH knows the situation with the spouse. The guardianship will get spouse completely out of it. Guardianship overrides POA.

Your mother still needs to file for Medicaid, either herself or through a power of attorney, but if worriedinCali is correct in assuming this might be about "spousal refusal," then your mother's husband (not a blood relative?) may just be waiting for the assets to transfer before filing.

In any case, you admit in your OP that you have never been involved, so perhaps your mom's husband knows what he is doing, and it is what's best for both him and your mom. Or... perhaps not. You need to talk to him to find out.

I agree. This is his problem. She already had Medicaid all he had to do was update info for the year.

I would not call the NH. Then they have ur number and they will hound you. As a child, you r not responsible for her care. (To members, please no filial law junk)

Do you think there is some cognitive impairment here. His has Medicaid paying her way and he thinks the children should be paying because he didn't want to fill out Medicaid papers?

The NH cannot legally kick Mom out. She has to be released to a safe place. I think the home maybe able to fill out Medicaid papers for her. There have to be other residents with no family they do this for. Just tell him no. If he gives out ur info to the NH, just tell them u have not lived with Mom since u were 12 and have no legal authority to help her. If he abandons her the state will step in as her guardian.

No, no, no. Do NOT SEND HIM ONE CENT!!! By doing that you are admitting you’re liable for the bill. Just ignore his demands. He is POA. It is up, to him to handle this.

Spousal refusal is legal in Florida. Have you contacted the nursing home to see if they can get her on Medicaid?

I would let them figure it out, don't panic, if he has done her Medicaid then I do not understand exactly what the problem is...many times it is just a lapse.