question

Charge flash usually means batteries fully charged and float mode. But doesn't fit here.
Are your panels connected in series or parallel?

Guessing 2 in series from your voltages.

Check the panel specs for temp compensation. It's a negative value as voltage climbs as temp decreases. Multiply this value by the winter temp difference from 25C. Add this to the Voc rating of the panels.

As you see 45V open circuit and assuming winter where you are, you're close to the controller input voltage limit. Might have blown the controller.

Try disconnecting the controller completely (panels first). Leave it a bit, then reconnect the battery. Then the panels.

If this doesn't work, check connections/wires/fuses to battery as well. But I think it's a dealer job.

Thanks Kev from Germany for your answer.

Yes, I have two panels ( Voc = 38.5V, Isc = 9.36A) in series giving 77V max across the 100V solar rated BlueSolar 100 / 50 unit.

I am using two string in parallel for a maximum short circuit current of 18.72A
The BlueSolar 100 / 50 has a maximum solar panel short circuit current of 60A, so I am well within margins of V and A from the panel.

Flash on Bulk lamp means: No solar energy going to batteries. (usually only at night)

Just now, this morning, in New Zealand, the summer sun was shining brightly, and suddenly, I saw that the unit's "Bulk Charge" lamp was glowing continuously, rather than flashing.
Happy was I ! " It has fixed itself".... I saw 750W coming into my almost flat batteries.

Then I did some toast, ran the microwave, and sadly saw that the lamp was back to it's flashing mode / zero charging !

I have not done a check of the unit's parameters. I will do that today. Perhaps it's settings had become scrambled.

NOTE: I was away from the house for 4 days, and only the fridge was going. Upon returning, that is when I saw it was not charging. Perhaps something funny happened in those days I was away ?