I just had the same issue. If you go to the marketing tab>all campaigns, go to the campaign but don't click on it.  Go to the three dots to the right and schedule the email from there. If you have already created the campaign and it's ready to schedule and go out, if you're not finished with it, i'm not sure what to tell you.    *I was giving me a different error code (something about fix account settings) when I tried to schedule it via this method, I did this 3 x (went to all campaigns and did the three dots, and attempted to schedule) and it finally worked. Not sure if I just got lucky, but I hope it works for you. ... View more