Could someone tell me please why VRF Mitsubishi outside unit PUHY-250YMF-C does not bother to start its compressor (the demand must be present as there is 30C with set point 19C in the space it serves) ?

When I switch power on, the 4-digits display on its pcb shows "8,8" (1-st and 2-nd digits) for about 15 sec, then "51" (3-rd and 4-th digits) for about 3 min, then for all the time there are "1" in the first digit and "1" in the 4-th one. Actually it is three PUHY' system - other two doing good duty for their spaces. The digits on them show also two "1"'s - only the first "1" takes the left vertical segment(s) of the first digit - while the problematic PUHY's one takes the right segment. The second "1" takes the right vertical segment of the 4-th dig at all units.

Have "belled" the windings - looks normal, 3-ph supply balanced, neutral Ok.

I knew nothing about Mitsub, let alone its VRFs untill today, am searching now internet for indications, deep switches settings, etc - with no success (Mitsi's motto : no money = no manuals).

Have read all threads about Mitsi's here - maybe, indeed, nothing to do to them without laptop with Mitsi's diagnostics software?