|First, try to configure only one mobile device with a fixed ip address of the range 192.168.2.2 to 192.168.2.99. I suggest to use this range, cause the router uses 192.168.2.100 to 192.168.2.199 for dynamic ip address assignment.|
If this works for the one device, try the next device.
Note: You must not use the same private ip address on multiple devices.
Use 192.168.2.2 for the first device, 192.168.2.3 for the second one, aso.
Don't forget to also configure default gateway and DNS server on that mobile device.
Otherwise, you will not be able to access the internet.
I guess the ip address for default gateway and DNS server is in your case 192.168.2.1.
The ip address range you posted (192.168.2.100 to 192.168.2.199) are private ip addresses, that are not accessable from the internet. This addresses are for your private network only.
So to be able to communicate with the internet, you need a public ip address.
While the ISP mostly only provides one public ip address, you need a device, that manages, that you can access the internet from private ip addresses with multiple computers or mobile devices over only one public ip address.
That's what a router does.