I just had the same issue with the 2021 Business on the 1065. After MUCH telephone time and music the only solutions were to add attachment?, check my RAM, my Processor, my Browser, etc. I kept insisting it was a software error and suggested this be noted and forwarded to correct department since there is nowhere in the program I can go to to report these kind of issues. Surprise, I was sent an e-mail link to this site. Don't think it'll be fixed anytime soon. Only solution is to print out return and mail it rather than e-filing because this counts as an error and it won't let you e-file it.
