One note to everyone that may helpful, may not for @EyesX problem but still:
Is that, if you are using cloudflare:
And since EE4 doing site setup, when confirming the site exists during SSL confirm stage, goes to check the site is up at a non-SSL http:// domain
SO: when setting up the site, make sure you have cloudflare SSL settings set to “Flexible” or the EE4 site site setup script will see site doesn’t resolve, and install will fail.
THEN one site is done setting up, now that SSL is active, you have to change cloudflare SSL settings set to “Full” or you yourself will get a blank screen
A little cloudflare niggle that i always forget until i see the blank screen!!
Hope this helps some folks