Cannot use realms due to failed html, showing 502 "bad gateway"

For some unknown reason the realms entrance page no longer works for me, this occur as a local issue on my PC only (another one in my household can log into my realm from another computer without problems). I have restarted the game many times trying out various settings and versions, restarted my computer and logged in using different accounts but the problem still remains. The entrance page looks like failed html displayed as text rather than graphics, entitled by the number 502 and “Bad gateway” within some of the html nodes