Fast forward to August. Our IT person has been communicating with Lacerte regarding the issue of the rejection of Form 990T because it needed Form 4136 attached (which it is by the way). Here is the latest communication from Lacerte:

"2020 EXM US 990T E-File Reject F990T-037 Looking for Form 4136
This unexpected behavior has been determined to be working as designed. Currently, Lacerte does not support Form 4136 for 990-T e-file. This return will need to be paper filed."

May I reiterate that we did paper file this return initially. We received a notice that it was not accepted because electronic filing is mandatory for this return. We send attachments to the IRS via Lacerte all the time. Why this particular attachment can't go is beyond me.