Incorrect connection parameters - IIS

Configuration :

Projeqtor 9.2.1
Windows server 2016
IIS 10.0
PHP 7.4.21
MySQL 8.0.25

Hello, I'm here to tell you my problem.

After having a lot of problems configuring PHP on IIS, I finally got access to the Projeqtor interface.

Once the configuration is done, I want to connect to the application with the admin login.

The database is well populated, all tables seem to be correct.

However, when I want to connect I get the following message:

Incorrect connection parameters

In the console of my browser I observe that the resource saveDataToSession.php returns an error 404. 

I also went to see in the logs of Projeqtor and here is the message it gives me:

2021-07-09 10:26:21.304 ===== TRACE ===== Login error for user 'admin'

My database is configured in utf8_general_ci.

I confess I am blocked and I don't understand where the problem comes from.

I hope you can give me an answer!

I looked in the IIS logs and this is what I found (see in attachments)

Unfortunately, this doesn't help me much. When I enter the full path of the files in my browser I can find them but it doesn't help me to find out how to fix the connection problem...