If Bubble’s standard robots.txt prevents Google from recognizing a bubble site, then that’s a problem that would be experienced by the majority of people with Bubble sites. (The standard robots.txt would block indexing of the test site, but no one should ask for their test site to be indexed).
To confirm that this was the problem, have you tried reverting the robots.txt back to standard and see if you experience the same issue? Also could you post a link to the forum entry that said robots.txt was the issue?