Create Site Not Working - Front end

Hi there,

I have a multisite running since before version 3.5 and since a few days the create site button on the front end of my site is not there anymore and also when using the direct URL doesn't work, redirects to main site homepage.

I already checked my network settings and I have "Both sites and user accounts can be registered. " enabled. Also tried with the default htaccess for subdomain network.

Maybe some advice or direction of solving this, before going through the disable all plugins and use default theme situation. I'm running a live network and I would like to avoid any disturbance for users on the network.