Your IP PIN is only for your own tax return. You cannot use your IP PIN to file your mother's tax return.
You cannot e-file a tax return for a past year with TurboTax. You have to file it by mail in any case.
Filing by mail will not take "forever." It will take a few extra weeks. You already waited more than a year to file the 2023 tax return. It should have been filed by April 15, 2024. So now you will have to wait a few more weeks.
The tag below your question says that you are using TurboTax Online. But you cannot use TurboTax Online to file for a past year. To file a 2023 tax return now you have to use the desktop TurboTax software for 2023. There is no free filing for past years.
A local tax professional might be able to e-file a 2023 tax return for you, but e-filing for a deceased taxpayer is always chancy. If the e-file is rejected you will have to file it by mail anyway.
