Why is my external flash (speedlight) not working on-camera?

I would like to use external flash with my Olympus OM-D E-M10 (mark I). It seems, however, that flash is simply not working with my camera. I have tried to set flash in camera to fill-in and fully manual mode, but no luck at all. Also I have tried different modes on external flash itself, including fully manual.

The external flash is Neewer Speedlight NW985. The only mode which is working is the wireless one where flash is triggered by in-camera flash.

What I can do to make the flash working? Is OM-D compatible with any hot-shoe flash or not? Which flash should I get if not? Or is my camera just broken? (It is possible, I bought it on ebay)

Also it’s interesting that in the moment I connect flash into hot shoe of my camera, it fires. Is this normal?

I am total flash-newbie, please be patient. 🙂

Fuji X-T2 troubleshooting: On-camera flash fires only once

this is an issue that has only started showing up and seem to point towards something physically wrong with the camera/ hot shoe somehow. The problem is any flash that I mount on camera only fires on the first shot, and doesn’t on any shot after. Turning the camera off then on again between shots is the only solution to use a flash currently, and it’s obviously frustrating and not the most practical solution. Even then, the shot isn’t properly exposed either. Same exact problem with both the Godox tt685f and the EF-X8.

Camera is in manual shutter and not ES, single shot mode and not in continuous or BKT mode, does the same thing in both manual and TTL modes, fully charged batteries in camera and flash, cleaned connector pins on camera and flash, flash confirmation on the left side of screen is visible (flash icon is not crossed out) so the camera knows it has a flash mounted. I haven’t tried updating camera and flash firmware, in the case of the Godox. I also haven’t tried using the Godox off-camera with a trigger yet.

I was using these flashes earlier in the year no problem which is the main reason why this all confusing and seems to point towards something broken in the camera somehow. Seems like something is stopping them from firing after that first shot. Just want to see if anyone has experienced this issue before, and has possible fixes before thinking about getting camera repaired. Completely baffled what is going on.