Gl-X3000 Sim Card Not Register

I bought this router and inserted a German SIM card. After many attempts and even changing the IMEI, I still can’t access the internet. It keeps saying that the SIM card is not registered. Could someone please help me? I’m not very experienced with this.

What SIM provider do you use?
Does the SIM work in a phone?

I found and fixed the issue. It turned out that I needed to attach all the antennas for it to work. Before, I had only attached two antennas.