Welcome to the community and thanks for posting. Sorry to hear roaming isn't working for you in Paris.
You mentioned it was working in the US a few weeks ago but I would still check roaming is active when you log into Your Account just in case.
Click on plan and device > Click the tab manage services.
Make sure roaming is set to on here. If it isn't move the slider to on and click update. This will present you with a green success message. It may take up to 24hrs for this to go live on your account.
You can also check the call barring option to stop calls abroad isn't set to on.
You could also try the following steps if roaming is on:
Turn your phone off and then back on again
Go into your phone settings and select a network manually.
Try removing your phone’s battery, while it’s still switched on – this helps reboot it and find a local network
When I was in Spain over the summer I had to turn my mobile off and back on again and was then able to connect to a network.
If after these steps you are still experiencing difficulties give our mobile team a call on +44345 600 789 from a roaming handset or land line so we can take a further look into this for you.
I had the same problem, but Virgin Mobile said that it was switched and so it was a problem with my phone. If happened next time I went to France I should do a factory reset. But this wipes all data off the phone.
Welcome to the community and thanks for posting. Sorry to hear you had trouble roaming when abroad.
Did you speak the team when you came back? I don't see a factory reset helping here. If you had issues while in the UK too then it's possible it could help.
There are 3 networks available which you can try to manually select from:-
SFR, Orange France and Bouygues Telecom.
If you have any doubts before you go then you can call the team again on 789 from a Virgin Mobile or 0345 6000 789 from any other phone. Alternatively, you can call the team from abroad on 447953967967 (if you have access to a phone).
Hope this information helps. Let me know if you have any further questions.