Why did the 403 Forbidden error suddenly appear after changing the theme of the site under 1s Bitrix?

Question

1C-Bitrix

I changed the theme on the site under 1s Bitrix, hosting timeweb, everything was fine, but after a couple of hours when checking the site it says:
Forbidden
You don't have permission to access / on this server.
I do not think that I could somehow spoil the index file, or change the rights to the folder, everything works fine on the LAN.
What else could be the problem?

Answer 1

With no rights

Answer 2

Look in the web server logs for what it swears at with a 403 error.