MODX admin panel not opening after installing SSL. What to do?

Question

MODX

MODX Revolution 2.2.6

We decided to install ssl on the site.
I asked the host to connect the certificate. I did not make any preliminary settings in the site panel, I already understood that I had to act according to instructions like https://wiki.hostpro.ua/knowledgebase/https-modx/ . I hurried, did not investigate the issue, never worked with ModX/PHP.

As a result, after connecting:
1) the admin panel page gives an error 500
2) the site on all mobile devices opens via https, on different desktops or via http, or via https.
3) some content such as carousels with sliders, menu links, content of some sections does not open.
There are two error logs:

[2020-12-04 13:27:28] (ERROR in xPDOConnection::connect @ /home/www/sitename/www/core/xpdo/xpdo.class.php : 2999) SQLSTATE[HY000] [2002] Нет такого файла или каталога

and

[2020-12-04 13:27:28] (ERROR @ /index.php) Error preparing statement for query: SELECT `modSession`.`id` AS `modSession_id`, `modSession`.`access` AS `modSession_access`, `modSession`.`data` AS `modSession_data` FROM `modx_session` AS `modSession` WHERE `modSession`.`id` = ?  -

I would be satisfied with a solution a la “return as it was” (you can live without https, as long as the site loads completely and the admin panel opens) - if it’s easier. Or how to make everything work with https. Thank you.

UPDATE. It turned out that the hoster transferred the site to a new server to connect the certificate.
After cleaning the cache, the site stopped opening in principle (error 500).

Answer 1

did you delete the core/cache folder?
You don’t need to edit any configs, only 2 settings are edited in the modx admin panel.