MPP Solar unit suddenly not detecting PV input

[TLJester]

Have had a dual 3048 system running for months.
Suddenly one unit is not detecting the solar array it is connected too.
Checked by flipping the panels to the other unit and it detects them just fine.
So clearly the issue is at the MPP Unit.

Both units are connected to 700w, 9amps, 80v, so well within MPPT range
(In fact output is currently 450w, 8amps, 54v today)

Not sure what i can do/test next to get this fixed. Any suggestions?

 

[Eber]

When it was not detecting the pv, did you happen to check the current? just curious if it resembles my problem.