MyBB Community Forums

Hi, all
I just build forum using MyBB on my localhost and then upload it to hosting with the address domain is https://alumni.smk-pws.sch.id. but when I'm trying to register as new user at https://alumni.smk-pws.sch.id is stuck at choosing username with red box alert. online forum MyBB using simplicity theme lastest version.
But when I'm trying register on localhost is can be done register as a new user, when I'm googling not all of the post can solve my problem (this case). I'm stuck at this point, and I'm attaching the screenshot image of the error.

Welcome to MyBB Community.

disable rocket loader & purge cache at cloudflare site
and then try again.

if above doesn't help then, assuming that you can login to forum admin panel,
run file verification tool from below location. what does it report ?
forum admin panel >> tools & maintenance >> file verification

ignore reported images & ignore files reported from install folder & its sub-folders

(2020-08-21, 02:05 PM).m. Wrote: [ -> ]Welcome to MyBB Community.

disable rocket loader & purge cache at cloudflare site
and then try again.

if above doesn't help then, assuming that you can login to forum admin panel,
run file verification tool from below location. what does it report ?
forum admin panel >> tools & maintenance >> file verification

ignore reported images & ignore files reported from install folder & its sub-folders

I already disable rocket loader and purge cache at Cloudflare but don't affect the forum, same as before, the username column still red when I'm trying to fill it. and when it runs file verification at the admin panel and comes up the box of 3 files has been changed. this the screenshot verification file.