The MeF Production system will be unavailable due to scheduled maintenance from 7:00 a.m. Eastern time, October 17, 2020 through 7:00 a.m. Eastern time, October 18, 2020.
I've tried e-filing twice since 7 am eastern time and it is still unavailable, and based on the IRS info at the link above, it sounds like that if returns aren't e-file by 9am eastern time on October 19th, you won't be able to e-file again until 9am eastern time on November 2nd.
"and based on the IRS info at the link above, it sounds like that if returns aren't e-file by 9am eastern time on October 19th, you won't be able to e-file again until 9am eastern time on November 2nd."
What I see at that page is that the Production System is Operational and that the Testing System will "be unavailable 9:00 a.m. Eastern time, October 19, 2020 until 9:00 a.m. Eastern time, November 2, 2020. The TY2020/PY2021 WSDLs, schemas and business rules will be loaded during this cutover. Please note: All existing test submissions will be deleted except for those sent in during the thirty days prior to cutover."
If you are not a testing entity, I don't see why you would be worried. If you are a testing entity, you should be glad that testing is beginning the cutover.