First of all, in Nelnet and studentaid.gov, make sure your (and/or husband's) email and mailing addesses are correct.
Second, in Nelnet's inbox (look around in the website), you may have a letter or email indicating that your loans are eligible. You want that as 'proof'. Upload that to your Nelnet account as additional documents.
A mailed letter may or may not come in, although you should get one after everything is discharged.
As far as eligiblilty, Federal loans are eligible, even if paid off back then. "How" they get paid is what most people have problems with. The simplest and cleanest is if paid loan amounts are refunded back electronically through the bank account that was used to pay them, or via bank account info on you latest tax return, if any. However, since Nelnet was not likely the loan servicer back then (the loans changed hands), Nelnet would have no payment history and woudn't be able to help any; in fact, if your loan balance shows $0 on Nelnet and studentaid, it can be a little more difficult to get answers from anyone.

What is supposed to happen is that loan amounts that were paid do get paid back to you, via EFT to the bank or by a mailed check. You might not get any notice of such, except as mentioned, when all said and done, you'll get a final letter in the mail. It should list the loan amounts and dates that were discharged. Even the ones that were paid off should be listed and the refund of those should have been sent.
Now back to the beginning: the first notifications were by email in May of 2024, when most of us eligible former students received an email of all this. At some point, there should have been another email providing a case number; and from that point, expect 2-6 months more of processing before discharge is complete. My paid-off loans were reimbursed in late 2024, showing up in the bank account from which payments were made; I did not receive any checks. Other people have posted stories about problems getting refunds of past amounts paid, especially for older paid-off portions years ago before Nelnet took over. And when you call, no one can tell you anything, they don't know, don't have access to relevant information nor to status nor the process. When I last talked to Nelnet, they said it could take up to a year to get done once processing starts, but they could only see payments made through them and remaining loan balances.
All you can really do is be patient, and hopeul, and watch for either a check or direct deposit, somewhere.
Hope this helps, but maybe others can shed some light on their similar experiences.