Thank you.
I have deleted the php.ini file via FTP from the root directory. It has resolved the issue. I appreciate your help.
Thank you.
Yes, our website is hosted with Siteground as well.
I had just spoken with tech support there, and was advised to post this incident here, as they are unable to resolve the problem. Their best suggestion was to bring it to the attention of the developer (here).
We have downgraded our PHP back to 7.3 for now, and it appears to be working. Whatever issue is causing this must be related to PHP 7.4 upgrade.
Let me know if you need anything else from me to address this. Thank you.