I have seen no reports of anyone having problems onboarding using Ecency. If you do have any problems I would suggest reporting in Ecency Discord #issues channel so that they are brought to the attention of developers who can respond.
I included a 3speak video in a post this week using Ecency app and it displays as expected.
I loaded the video to 3speak using my Ecency video gallery in the app and was able to choose the thumbnail that I wanted displayed.
I'm happy to help and can find answers to any questions that you might have.