Is it okay to cross post questions on MO and MSE anymore?
How about ask a question on MSE after posting on MO but not getting answers, or vice versa?
Short answer : no.
(By the way, it has never been "okay" to simultaneously cross-post questions on MSE and MO. We've been requesting users to stick with one site and wait for a reasonable amount of time before trying to ask on the other site.)
Longer answer: As of today, a question that you may want to move between the two fora now can be properly migrated! The usual rules apply (only questions less than
a month two months old can be migrated directly, other requires intervention of a higher power).