Facetime is a big problem

Hello May I know why the facetime calls are not getting through. When I trying to call my mom India from germany she didn't even get notified and the call is not poping out on her ipad. this is the same case my brother who is calling from USA. before 13.0 IOS everything works fine.after upgrade to 13.0 to 14.1 IOS this problem still persist. Can anyone help me on this. Also adding to this Apple didn't done good IOS patch for facetime calls,when we add someone to existing call its auotmatically moving existing caller to ringer mode and no able to see them.Please help me in this regard.

Regards

Manoj