Changing country: ok at first, and no internet after a restart

Hi, I'm new here, and my level on network is about 0!
2 years ago i bought a DWR921, picked up RS232 on, and changed with your good OPENWRT, with firmware V19. I'm using the DWR in a motorhome, for internet wifi broadcast from 4G antenna, and to discuss with an Arduino (for SMS). It's work perfectly in France, even i passed the Spain border, in May and this July travel.
In the two cases, after a voluntary shutdown, the internet connexion is lost... and cannot be restored.
Yesterday, i upgraded the firmware to V21.02.3, imported connexions (proposed by system), installed some prk as Picocom, throw my internet phone connexion (by Wifi bridge).
I looked for topics on OpenWRT for troubleshooting, but it's a little bit hard for me.
I don't understand where i can identify roaming for cellular communication data?
I discussed with the Qualcom 4G chip in AT commands: SYSINFO and CEREG show clearly me that connexion is Ok in 4G, with roaming. It shows me too that no packets pass throw the router...
Is anybody can help me? :face_exhaling: :cold_sweat: