You need to provide some information about your environment, if it’s Linux or Windows underneath, what type of web server, the version of OpenEMR in use, MariaDB/MySQL, PHP, etc. To start with, you’ll want to look at the error logs on your server, (typically /var/log/apache2/error.log, depending on the details of your particular installation).
Have you checked the contents of your error logs? You still haven’t stated what version of PHP is in use, if it’s a XAMPP install or other setup. (Bizarre as it sounds, I have seen OpenEMR installed on Windows using just MySQL & IIS, it was painfully slow and awkward, but it was technically functional). Make sure that you are using one of the PHP versions compatible with 7.0.3 (PHP 8l.1 through 8.4). You are probably going to find entries in the error log informing you of a missing module or problem with your PHP configuration.
Also experiencing this, but only when navigating to “week” view. day and month work as expected.
the logs I am seeing in var/logs/apache2/error.log are PHP Parse error: syntax error, unexpected identifier “the” in /var/www/localhost/htdocs/ope3/%%ajax_template.html.php on line 238, referer: http://:8300/interface/main/calendar/index.php?module=PostCalendar&viewtype=day&func=view&pc_username=admin