In-Plan 401k Conversion Deadline

On Dec 30 2021 I did an online In-plan 401k Roth Conversion with Pre-tax money.  Online the Trustee confirmed the conversion for  2021,but did not send a 1099.  My online account shows the Conversion for 2021.  I later received a statement confirming the Conversion for 2022 instead of 2021, so no 1099 for 2021.  I messaged them about the  issue, but was told  call.

 

What is the IRS deadline for an In-Plan 401K conversion ?  

Are there any procedures or regulations I can refer to when I call the Trustee to have them issue the 1099R for 2021 ?