Apple Watch Ultra NOT working properly with Optus Numbershare

I upgraded my series 6 watch to an Ultra, and after I activate cellular data, it works for about 12 hours, then deactivates itself, and data can't be used. The watch app says this:

I then remove e the cell plan and try to reactivate it, and the F%$#&N thing spits this screen at me:

[Edited by Moderator]