Reverse proxy does not work on synology nas installation. Please help

[MHReijnen]

I installed nextcloud-aio following the instructions on this site in my synology NAS. I can get to the installation menu via my local network IP on port 8080, but installation hangs on this error: "Domain does not point to this server or the reverse proxy is not configured correctly." I looked at the instructions too which I was directed, but I can't find a fault. Can someone please help? I am not very familiar with computer code, but I can manage most of the time with some logical thinking and help from the internet. This time I really need help.

nextcloud-aio-domaincheck.json
nextcloud-aio-domaincheck.csv
nextcloud-aio-mastercontainer.csv

nextcloud-aio-mastercontainer (removed keys).json