Fatal error: Class ‘WP_Customize_Section’ not found

I had the same issue.
Luckily I keep old backups on my PC.
The usual route is to rename your Acivated Theme Folder to something other than OceanWP-Child. Usually you would rename it with a full stop after the original name, then add a suffix, I use “old” but you can use whatever you wish.
So in your FTP your folder will be in /the name of your website/public_html/wp-content/themes
Then in the themes folder you would rename, OceanWP to OceanWP.old Or if you are using the OceanWpchild (I strongly suggest this) oceanwp-child-theme-master.old

Now, this didn’t work for me, even after I cleared my browser caches and cookies. I altered my htaccess file to use a default theme OTHER THAN OceanWP and this, again, didn’t work.

What I had to do was, upload an old version of oceanWP, via FTP and this allowed me acces back into my admin area and website.
Upgrading back to the newer version, promptly broke everything again.

THE ERROR::

Fatal error: Uncaught Error: Class 'WP_Customize_Section' not found in /home/customer/www/XXXXXXXX/public_html/wp-content/themes/oceanwp/inc/customizer/library/customizer-custom-controls/inc/custom-controls.php:46 Stack trace: #0 /home/customer/www/XXXXXXXXXX/public_html/wp-content/themes/oceanwp/inc/customizer/library/customizer-custom-controls/inc/customizer.php(6): require_once() #1 /home/customer/www/XXXXXXXXXX/public_html/wp-content/themes/oceanwp/inc/customizer/library/customizer-custom-controls/functions.php(274): include_once('/home/customer/...') #2 /home/customer/www/XXXXXXXXXX/public_html/wp-content/themes/oceanwp/functions.php(269): require_once('/home/customer/...') #3 /home/customer/www/XXXXXXXXXX/public_html/wp-includes/class-wp-hook.php(303): OCEANWP_Theme_Class::classes('') #4 /home/customer/www/XXXXXXXXXX/public_html/wp-includes/class-wp-hook.php(327): WP_Hook->apply_filters(NULL, Array) #5 /home/customer/www/XXXXXXXXXX in /home/customer/www/XXXXXXXXXX/public_html/wp-content/themes/oceanwp/inc/customizer/library/customizer-custom-controls/inc/custom-controls.php on line 46

Hi, Shahin

I followed your instructions, to the letter, right up until the
“​5- Head over to your website dashboard > appearance > theme and make sure to activate the correct theme.”
Part.
I couldn’t get on to my website dashboard.
Fatal error: Uncaught Error: Class ‘WP_Customize_Section’ not found in /home/customer/www/XXXXXXXXXX/public_html/wp-content/themes/oceanwp/inc/customizer/library/customizer-custom-controls/inc/custom-controls.php:46
and such like.

I now have to manually upload an old version AGAIN, and start AGAIN.
I have noticed though. I can only access the website after I have logged into the Admin page. If I try to access the website without, doing so, I get the error.
I’m hoping it’s because that page has been cached and it needs to catch up.

I keep daily backups of database and website.
The only way I could get my website back…
1. Open FTP, click on public.html folder and delete the whole folder and contents.
2. Whilst that was deleting, i went onto my hosting page to access my database and deleted that.
3. When public.html folder was fully deleted, install a backup from “BEFORE” the update.

Everything now works but until i can be sure the update won’t break my website again, i WILL NOT be updating it.

****NOTE****

This was a DRASTIC step to take, as the website had been off for over 48 hours and losing me potetial customers and custom. Deleting the WHOLE of the public.html folder is not really necessary, as the affecteed files would only be in one or two folders but I had been on the issue all day and was getting very frustrated with it.
Again, deleting the entire database is also not necessary but being unsure on how deep the issue was, it was easier to bin it than fix it.

Also, my backups replace ALL the files that are not there, they do not, however, delete the files that are already present. This is why I deleted the whole of the public.html folder. ensuring the corrupt files are gone and the backup is guaranteed to work.

I’m not a coder and staring at coding all day won’t fix anything so I came up with a soluion that I could do.

I do not recommend these steps UNLESS you are 100% sure your backups included your database AND whole website.

@petitcuenotc You were lucky, some people do not have things like jetpack, I personally find it intrusive and annoying.

Thanks @shahin,
I just installed version 3.1.1 and everything is fine. No more souvcis. So for those who have the problem switching to 3.1.1 is good.

@kiefels @goajazzz