Thank you for your response and suggestions. When we upgraded from 2023 to 2024, I left QB 2023 on the hosting computer for a bit while we ensured there weren't issues with 2024. Then a few days later, I uninstalled 2023. I notice now, however, that remnants of 2023 are riddled throughout the computer - users, DB services, etc. I have disabled and/or deleted those as applicable. 

Although my firewalls already had the QB directory set as an exclusion, I added a few more exclusions as well. 

Today things have operated correctly. Will give it a few more days to see what happens, but regardless, next time I am there (I work remotely out of town), I will uninstall 2024 from all computers, ensure 2023 was also fully uninstalled from all computers, reboot numerous times, see if any remnants are left that need to be removed, reboot numerous more times, and then do a fresh install of 2024 ensuring the steps to configure multi-user access for current versions meticulously,  as opposed to assuming they've remained the same over the years. Additionally, I will ensure all of your suggestions have been followed. 

If I have any issues after that, I will definitely contact tech support and try and wrangle my way to someone who has the expertise needed.