Failed upgrade to 4.0.x from 1.5.6.4

Hey, so i have website which shows blank page. I've tried to install the newest addition to the website but to no avail. Therefore, I decided to back up the folders i have to the old one which ended up corrupting the website (didn't know that the database structure updates as well). I have other websites that run the same old engine, so i copied the structure used in these databases to the newest one, got the data back in place which fixed the errors. But now the main page displays a blank page which doesn't tell me anything. The admin dashboard loads up nicely with all the orders and tabs working. What I've done so far:
Emptied the cache on all the possible locations, including vqmod cache.
Since i have vqmod, I reinstalled it, I've seen it is recommended to do so.
Tried enabling error_reporting(E_ALL); and ini_set('display_errors',1), which still doesn't show any errors
Also tried disabling plugins one by one to see if any influence is done
The only error i see in console is the favicon one.
My PHP version is: 5.6
Opencart version: 1.5.6.4

Check you host to see if they have a backup of your files and database from before you made changes. Most hosts will take daily backups.

Otherwise look in your server and PHP error log, not just the OpenCart one. Ask your host if you don't know where to find them.

This was done a few weeks ago so the backup is not available anymore :/ I've managed to upload the website to localhost and managed to see some errors. Adding images to the reply. By the way how hard would it be to launch a new installation and upload old data to the new installation?

The first error is a problem with an SSL certificate. The second is an issue with a vQmod extension.

Hi, how much data do you want to retain?
Product and Category Data
Customer and Order Data
Extensions and Customizations

sull1van wrote: ↑

Thu Jun 08, 2023 10:11 pm

This was done a few weeks ago so the backup is not available anymore :/ I've managed to upload the website to localhost and managed to see some errors. Adding images to the reply. By the way how hard would it be to launch a new installation and upload old data to the new installation?

Please take note there are numerous features that can be imported into the new installation but other data that may either need to be imported manually or not at all.