G4AR Gateway external antenna use

I have been helping a friend get better internet access at a fairly remote lake house in upstate NY.  Over the last year, we were using a Cudy P5 5G cellular router with a T-Mo 5G hotspot SIM.  The router was locked onto band N71 for 5G, and we saw download speeds of 80M with uploads of 8-10M.  This was working very well, except for the monthly data cap that they kept hitting last year.  When this new T-Mo router came out with the external antenna connectors, we jumped at the chance to get the unlimited Home Internet service for them to use.  I just installed it, with the same 4x4 MIMO antenna array that was connected to the Cudy router.  But I only see 18M download speeds and 1-2M upload speeds.  This device is not connecting via 5G on band N71.  It is only connecting via LTE on band b12, despite nothing being changed with the antenna array.  Does anyone have internal connection ID's for the Ant 1-4 external connectors?  Typically they are labeled on the main circuit board as d, m, m1 and m2.  I would like to not have to try 16 different combinations of cable to port settings to get the optimal one (that might allow the device to start using 5G service?).