Why is turbo tax requiring Form 5329-T and it won't let me do anything with it?

TurboTax does allow for Form 5329. -T stands for Taxpayer.

To edit these details, return to the HSA interview. See: Where do I enter my HSA contribution?

The tax paid for keeping excess contributions continues until the excess is removed. Contact your HSA custodian before July 15, 2021 to request the withdrawal of excess contributions for 2020. 

If you do not think this applies to you, you will need to recheck your input and be sure that the contributions and distributions are reported properly, including what amount of medical expenses were paid by the distribution.

Click the article for more details:

For the TurboTax entry: Why am I showing an excess HSA contribution?

 2020 IRS Publication 969 Health Savings Accounts and Other Tax-Favored Health Plans