Just a moment, please screen with php8 and working ok with php7.4

with a simple project without much of code, it works with php 7.4 but fails using php 8 with " Just a moment, please " screen and stuck there,
and there is nothing in the log files except a line .
15-12-2021 06:09:01 Scheme Request URL start: https://heserver/abc.php

Can anyone bring some light into what I am facing now.

And in the PHP error log?