I'm getting the same issue as well when trying to submit 1701Qv2018.
I already tried reinstalling the eBIRForms app, restarting my computer, connecting to the other network, and trying on a different computer, but still getting the same error.
I have been using the app for years and this is the first time I encountered this kind of error.
Does anyone else encountered this kind of error before? and if yes, how did you fixed it?