I am unable to transmit my 2018 tax return.

[phpardel]

The [Transmit my returns now] button is locked.

[Critter]

Try clearing your cookies and/or switch browsers.  

[Anonymous]

some other things to check.     did you override anything on the return? TT doesn't a;;ow efile when you override an item. ?

go to the review tab to make sure there are problems such as incomplete items which would prevent filing.