IRS e-filing was shut down on January 12.  LC/Proseries accepted the extension, then held it, then will file it when e-filing reopens. (There were notifications to all users in December and early January that you should have read. These notifications appeared to me when I opened Lacerte)

 TODAY THE EXTENSION MUST BE PAPER FILED.

@Dham 

Solved: IRS Business E-File Live January 16, 2024 - Intuit Accountants Community

won't process until tomorrow

You mean the IRS closes?  Who would have ever thunk that.  

January 16 is the deadline because of MLK day! I have not got MLK off in decades, so the additional day escaped my mind.

Yeah, as tax practitioners, we forget about holidays between January 1 and April 15.