I have a RUT950 with a T-Mobile 4G sim card. The connection works great initially.
However, after 24h, the IP address is renewed. From that point on, the internet connection is lost. However, the Teltonikia interface still shows that mobile data is connected. I cannot ping any domains. I also SSH'ed into the router and tried ping from there (1.1.1.1 and 8.8.8.8), but no reply at all.
Interestingly, the only thing that seems to be working, is doing a DNS request (using nslookup for example). This suggest that the data connection is fine. The firewall configuration is default. I also inspected the logs thoroughly but coundn't find anything suspicious.