By default, the bridge is connected over the WAN zone. You will need to allow access on RUT2 from WAN (in this case, RUT1). Please, take a look at this post here. Since the device is connected to another AP in bridge mode (so there is no other WAN sources on RUT2), you can set Input/Output/Forward on the WAN zone to ACCEPT. You shouldn’t get any errors like the person had in that post, but if you do, you can take a look at this post here.
Many thanks for the support. May I have any option to access and change RUT2 config remotely from RUT1 cli? Or given the default settings I need to physically reach RUT2?