EX6200 cannot add 5 GHz band

I have had this extender since  2015 and had no problem with it until I recently changed my service provider (from Comcast to Sonic Fiber), which prompted a need to re-connect the extender to the new router.  However this time around it won't connect to the 5 GHz band (using the WPS buttons).  I had no problem connecting both before, but now the extender only has the 2.4 GHz light on.  I checked on the router admin page which confirms that both 2.4 and 5 GHz WPS are enabled so I assume it is the problem with the extender (or compatibility issue?).

Any suggestions will be appreciated!  It is driving me crazy!