What are you trying to do? What specific error are you getting?

For the 1099-R entry: Line 2a is the taxable amount of the distribution and would be less than or equal to box 1 Gross Distribution.

Line 2b you can leave blank since you do not have a form.

For the 4852- line 8 is literally every numbered line on the 1099-R. Here is the Form 4852.

Instructions for Forms 1099-R and 5498 will show you the box 2a information requirements.

I was told the 4852 form will be downloaded by 2/25/2021. I still have not received it

The form 4852 is a last resort. This is what the form says:

 If you don’t receive the missing or corrected form from your employer or payer by the end of February, you may call the IRS at 800-829-1040 for assistance. You must provide your name, address (including ZIP code), phone number, social security number, and dates of employment. You must also provide your employer’s or payer’s name, address (including ZIP code), and phone number. The IRS will contact your employer or payer and request the missing form.

Because of this, you cannot e-file a return with a 4852, it must be mailed in.

Good news and bad news. The form is listed to be released today but it not yet showing the word available. When it changes from a date to the word available, you will be able to use the form.

The IRS works on forms from most common to least common. See Federal form availability for expected release dates. Once released, we work to incorporate them quickly.

it shows available now, but the program still says it will be available soon and prints it with the watermark "Do Not File ...".

This happens after I try to update the form.

I received an email 2/22/2021 from Turbo Tax stating Form 4852 was ready for download. Wednesday, 2/24,  I was told that the programs would have an update including  the Form on Thursday 2/25. As of a few minutes ago it still isn't available. When????? I have done everything in my power to get the employer to supply a W-2 but they are ignoring me and about 50 others in the same boat. I would like to get my refunds and Turbo Tax isn't doing its part. WHEN??????????

The paper version from the IRS has been available for about a week. As of a few minutes ago it still hasn't been included in an update from Turbo Tax. I'm still waiting, too.

Interesting. I received an email from Turbo Tax stating Form 4852 was ready. As of 5 a.m. 2/25/2021 it still hasn't been included in any Turbo Tax update. So, WHEN. I've got refunds coming and would like to have them real soon and this is holding me up.

Have you tried to run a manual update of your software to see if that will load the new forms?

@JohnF219

The software update came one day (the 26th) after the form was flagged as available. The update took care of it, and e-filing also worked for me today. TurboTax should not put a date of availability which is earlier than the software update. This is quite frustrating. The postings  of Experts that don't know the correct answers are also frustrating (see below).

This will  be useful for everyone for  next year's filing:

The turbotax forms page Federal Individual Forms Availability (intuit.com)  has wrong entry: