My iphone can't connect to my network after updating to ios 14

Ever since I updated my iphone 11 and ipad to ios 14 a few days ago, I have been having continuous problems connecting to my home network. I own an Orbi RBK 53 router with 2 satellites, and I get an eas.outlook.com cannot be verified message. When I check the details, I get the following: "routerlogin.net certificate not trusted". This is my router's certificate, and it is supposed to be valid until 2030. I had no problems whatsoever before updating to ios 14 so, there has to be some kind of incompatibility with the new ios and my router. Needless to say that I have a couple of older ipads and a laptop, all of which connect to my network without any problems. I have already rebooted the router several times, I have also reset network in my iphone and ipad, and everytime I take any of these actions, I regain connectivity for a few hours, but the problem returns.

Can anybody suggest any fix?