Last reharsal my guitar simply stoped working in the middle of a song, after like 5 seconds that I turned off/on it started to work again but then after 2 songs it stoped working again, this time turning off/on didnt solve the problem, I was despered, checked all cables and everything was fine, then sudently started to work again until the last songs of the reharsal, without I doing anything (?). When it happened again in the last 2 songs, the bassist said "man you amp is blinking", and I saw the display flashing for a couple of seconds and then the sound stoped again.
I've tested the power outlet, speaker cable, power cable and guitar(p10) cables, they all working fine, seems something on the amp. Next month my band got our first gig to play, in a small open air party, and I'm afraid it will happen again, bcause last month it occured 2 times, but turning off/on solved the problem, this time dont.
I'm from Brazil and I don't know if you have customer support here, I imported my amp from another country(didn't find any oficial store nearby to buy on Brazil).
You can try doing a factory reset and restore the latest firmware (make sure you backup your patches so you can restore them later).
What type of cab are you using, what is the impedance?
If possible can you try a different speaker cable and maybe even borrow a different cab to try? it's possible there may be an intermittant short circuit happening in either the cable or the cab that's causing an issue, it may only happen when the speakers are being driven.
Beyond that, there is pretty much nothing you can do other than getting Marshall to repair it.
I have the same problem and the display is getting dim now. I analyzed that it depends on the electrical network. In the place where testing depends on the time the problem returns. Has anyone fixed this yet? I'm from Brazil too