@XceptDev You could try connecting the TL-WPA8630 directly to your modem via Ethernet cable, then connect other client devices to the TL-WPA8630 to see if internet works.

@RMB57 When the issue happens, if you just restart those units, will they work again? I suppose they can be affected by powerline interference, so move electrical appliances away from them, and also...

@DaveFX To set up the router, you could refer to How do I log into the web-based Utility (Management Page) of TP-Link wireless router? to log in its web interface. However, I don't think you are able...

@caste Internet IP on the router differs from your public IP, which means you are behind a CGNAT, in that case, OpenVPN Server will not work remotely, same for the PPTP VPN Server, you'd better check...

@yugi888 If your device is not locked to a specific operator, it should support oversea SIM cards as well, just make sure the LTE bands are compatible.

@ALAMINAM Thanks for sharing!