impossible to pass first time authentication for /?admin

[mikekgr]

Describe the bug
In my Ubuntu 20.04.6 server that has php 7.4.3 and nginx 1.18.0 I tried to install snappymail inside my /var/www/html/snappymail and although everything goes fine, I followed the instructions: https://github.com/the-djmaze/snappymail/wiki/Installation-instructions#general-instructions
I opened the admin page in incognito window of my Google Chrome browser (Windows 11), then I copied the first time admin password from data/data/default/admin_password.txt and tried to logging as admin with the specified password.
No matter what I did (e.g. I did refresh the admin page to get new admin_password.txt each time, I restart nginx, I reinstall (clear install) in different directory etc) ALWAYS I got: Authentication failed
What I am doing wrong ? What to check? I found snappymail very good for my need and I want to install, preferable to upgrade my rainloop to snappymail.
I also tried to upgrade my rainloop installation but I faced the same problem (Authentication failed).

Please complete the following information:

• Browser: Google Chrome Version 131.0.6778.265 (Official Build) (64-bit)
• IMAP daemon: dovecot 2.3.7.2
• PHP version: 7.4.3
• SnappyMail Version: latest v2.38.2
• Mode: standalone installation using snappymail-2.38.2.tar.gz from github

I am willingful to check whatever you want in order to trap the problem. Keep in mind that the latest version of Rainloop (1.17.0) is working fine.

Thanks.

[mikekgr]

is there anybody to help me with this problem? Mayby the developer of snappymail @the-djmaze ?
Please help me, thanks.