FaceTime on iPad while connected to iPhone hotspot

hi,

I'm sure I used to do this with no problem but now it won't work for me.

here's the situation, I work away from home and stop in hotels with crappy wifi and phone reception so what I do is put my phone on the window ledge so I get 5g then use my Mac or iPad connected to my iPhones hotspot, then FaceTime home to my wife and child using my iPads FaceTime but just recently its not working it says "iPad must be connected to the same wifi network as iPhone".

I'm nearly 100% I've done this in the past but for the life of me of me I cannot get it to work?

Any ideas please guys?

thank you!

[Re-Titled by Moderator]