bertvz,
You can do your own diagnostics as to where the problem may lie. From you PC/phone, first check IP address to see if you got one for DHCP. Usually a 192.168.0.X, except .1 & .2 (those are reserved or allocated to indoor and outdoor router).
If good, then ping .2....that should be your indoor router (just converts Ethernet into Wifi). If good, try ping to .1...this is the outdoor router.
If all good, you need to login to where you think the fault is. Try .1....Look at the menu and find the wireless section. See if the router says "connected", and what the signal levels of the LTE signal is. Look for things like RSRP, Q & I. They should have values like -70 dBm is good signal, < -100 dBm is bad signal, but should still provide connectivity.
If you can follow above, you should be able to figure it out. If not, google's your friend!