EPIC Games Launcher stuck directly after start

Hi, on both Mac Mini (Late 2018) of my kids the EPIC Games Launcher started perfectly and the kids could play Fortnite. Since a few weeks (don't know the specific date) the EPIC Games Launcher tries to update without success. MacOS is up-to-date, internet connection is up and running AND we tried to start the EPIC Games Luncher on our iMac (Late 2015) and the Mac Book Pro 13' (2016?!): no problem, the software updates and runs perfectly in the same network environment. I already deleted one Mac Mini completly, erased the SSD: same issue. I tried to copy the files from the Mac Book Pro: no success. I had a VERY lenghty conversation with EPIC support: they concluded with: speak with APPLE, we can't help you. It would be great if anybody of you share their problem solving, in times of quarantine a game is for the kids quality time...

Best wishes

Syberian