Hello,

All of a sudden, notifications stopped working on d2jsp. I've cleared cache, browser history, etc. I've restarted, reloaded, etc. Nothing seems to fix it. After disabling and re-enabling / re-registering notifications, the first one sent gives a "404 not found - nginx" error on https://forums.d2jsp.org/null.

Is anyone else having this issue? Is there something I haven't done or tried that can remedy this?

You can reinstall your browser or try another.

I tried that. I installed Chrome and the exact same thing happens.

Is for a phone or pc?

PC

Check you have latest updates for your browser and pc.
Restart your PC, this will restart any services that may have stop working.
Check Focus Assist/Do Not Disturb: Turn off "Focus Assist" or "Do Not Disturb" in the notification settings to ensure alerts are not being silenced.
Enable system notifications: Go to Settings > System > Notifications and make sure "Get notifications from apps and other senders" is turned on.
Enable background apps: Some apps require background activity to send notifications. Go to Settings > Privacy > Background apps and turn on "Let apps run in the background".

Completed all of these steps and still no changes... still doesn't work... still gives the 404 not found. Notifications used to work seamlessly with no issue then stopped working with no updates or PC changes at all.

Guessing you are using IE or Firefox, since you said you tried chrome.
Could you try removing your devices in push notifications and adding just your PC. The 404 error is a client side error when trying to reach a server fails. Usually from incorrect url or it can't find and is missing or file moved.
Test this before trying any below.

Restart the Windows Explorer process: Open Task Manager, find "Windows Explorer," right-click it, and select "Restart".
Run a System File Checker (SFC) scan: Open Command Prompt as an administrator and type sfc /scannow, then press Enter. This can fix corrupted system files.
Clear the notification cache: Go to the C:\Users\%username%\AppData\Local\Microsoft\Windows\Notifications folder and delete the contents.
Restart the Windows Push Notification service: Open Services (by typing services.msc in Run) and restart the "Windows Push Notification System Service".

Restarting "Windows Explorer" worked! Thanks for taking the time to troubleshoot this with me

No worries, thanks for being patient. Glad you got up and running. Gl Hf <3, have a wonderful rest of your weekend.