How to I change my WPMU location (Database problem)

Greetings,

So I'm trying to move my WPMU network from the test location (www.ageneve.net/v15/) to the production location (www.ageneve.net).

I'm pretty sure I followed all the instructions given there : https://premium.wpmudev.org/blog/how-to-move-wpmu-to-a-new-domain-the-simplest-guide-ever/

However, after uploading the files and the modified database (and updated wp-config and htaccess), I have an error message saying "Error while trying to connect to the database" (the message is in French, I'm translating).

I double-checked that my entries in my wp-config.php file are correct and it is so, so I have no ideas why that problems happens.

I tried the whole process a few times more, with each time the same results.

Any idea of what I should do ?

Thanks a lot in advance. I'm a bit worried cause we only have a few day before the deadline.

Thanks in advance for your help,

DJ