OS Catalina Windows not showing in start up disc

[Roxy.music]

I have just updated to OS Catalina (10.15.And in the start up disc no option for my external T5 ssd with Windows 10 with boot camp on it?I tried the other way of getting it on here option .key all went well untell i tried to log back into Mac i got this message *Can,t find Boot Camp*? i know that this seems to happen a lot.Have they stoped the start up disc being windows on
Catalina ?

 

[IowaLynn]

removed

 

[Roxy.music]

Surely someone must be able to help me with this problem.

 

[Roxy.music]

I tried it with a backup from Mojava it showed om the start up disc ,when i tried to get back to OS it showed d this message
*Could not locate OS X Boot Volume *
there was another thing to on there asking which drive did i want to go to it was the backup drive i had just been on.When i went straight to Windows there was no box for Catalina

 

[Roxy.music]

Windows with Boot Camp and everything was fine until i installed catalina in System Preferences -> Startup Disk my windows partition was lost and when I want to switch to my windows must restart my Mac Mini and Press Down option during startup. I can't switch directly from OS X.
Hope that explains it better. Plus the fact I got this message when trying to get back into Mac os from Windows *Could not locate OS X Boot volume*I have looked online but no one has the answer.

 

[rumormiller]

I'm using Catalina I hold the option key on boot to select windows 10 on an external SSD or macOS on the internal drive. I believe that's the only reliable way to switch between the two.

 

[Roxy.music]

Up till I updated to Catalina it was working fine on Mojave from start up disc system Preferences