Unable to watch downloaded videos on my new iPad (A16) with iPadOS 18.5 outside when using a different Apple Account

I have 18.5 version , was told by an agent to try a different account I asked about the 90 day clause whereby you can't change the downloaded videos (he didn't know what i was on about), but said it won't make a difference in this instance, but it has and now I only have afew downloaded videos that I still can't watch when out

[Re-Titled by Moderator]

Original Title: Bought new ipad A16 cannot watch downloaded videos when out, I have contacted apple support 5 times now I cannot use it at all as they suggested trying a