@Filip123 EX220 is an ISP router, most probably with a customized firmware for your ISP. This could be the reason after resetting, its wireless SSID to be the same as before. For more details on that...

@Serse Ideally, your wireless settings should look like this:

@Serse One possible reason could be the distance between the MR200 and the boiler module - here are some advises for placing the router. Another reason could be the using of Smart Connect feature -...

@Akhilrajaman Try Dynamic IP address then. If that doesn't work for you either, your ISP probably is using a PPPoE connection. You may contact them for the details.

@Cludi75 The easiest way to resolve this, assuming the reason is the FW update of MR505, is to downgrade the MR505 to the previous FW release.

@Kameh Use this guide to troubleshoot your issue.