Hello I have finished redesigning my site and I have moved it to the main directory of my host but it has gone blank.
Now I have returned it to its previous directory but the error persists.

Error when I try to go to admin:
[06-Dec-2021 09:27:51 UTC] PHP Parse error: syntax error, unexpected '?' in /home/mysite/public_html/v2021/plugins/system/regularlabs/regularlabs.php on line 188

Error when I try to go to the main page:
[06-Dec-2021 09:39:02 UTC] PHP Parse error: syntax error, unexpected '?' in /home/mysite/public_html/v2021/plugins/system/regularlabs/regularlabs.php on line 188

I already tried to rename the folders of the plugin and the library but it does not solve it and it gives me other errors
Thanks in advance for your comments.

My Joomla 3.10.3
Cache Cleaner 8.0.1
PHP 7.2

I did what you recommended and I was able to enter the backend again and try to install the plugin but it does not allow its installation and it shows me an error:

Error Clear Cache will not be able to work.
The Regular Labs Library plugin is not installed.
Advanced Module Manager will not be able to work.
The Regular Labs Library plugin is not installed.
This extension is not compatible with PHP Cache Cleaner.
You need PHP Cache Cleaner or higher to install and use this extension.
Error installing plugin

I have noticed that my modules managed with Advanced Module Manager are not available now 🙁

I leave you my access data, please let me know if you will enter so that I do not do anything else and thus avoid generating another problem:

if i have php 7.2 you can check it in cpanel 😉

It is very strange, so why did it allow me to install and work with it without problem? this came up as i mentioned earlier by moving my site from subdirectory to main directory

I just moved my last .htaccess to the main directory and now I see the whole site again, I think the key was that in the current .htaccess I did not have the php 7.2 activated 🙁 I want to ask if it is safe now to reinstall the cache cleaner plugin?