If somehow the formatting of the the area where the OS boots has any corruptions, updating firmware may not cure everything. If the RC is up I would use a pc or mac and Assistant2 to factory default it. That causes the DJI/Android recovery kernel to boot and reformat and load the default which should straighten out any wifi issues if it's not your router denying connection, but I suspect you would know if you have had similar issue before with your router. If not then it is the RC and likely an Assistant2 default and reload should do it.
Just saw this.... Will try later this evening.
See the pic... This is all I get.