I can't receive challenge requests

JL, I know you've checked already, but I just had to remind myself what my settings were. I found them using the cog icon at the top right of the screen then selecting "Gameplay", and then "Challenges". I've set everything to be as open as possible. Do your settings look similar?
Pics attached.

Yes, i can't post attachment here either, but i have gone to the same page you mentioned.
Here's my settings:
Allow Challenge: ✅
- ✅ Everyone
- ⏹️ Only Friends
- ⏹️ Nobody (rematches are still allowed)
Incoming rating
Set the rating range for players who can send you challenges.
- min: [∞] max: [∞]
Outgoing rating
Set the rating range for who you can challenge.
- min: [∞] max: [∞]
Ignore rating settings for friend challenges: ✅
Offline Challenges: ✅
Allow challenges when you are not in Live Chess. You will be alerted via the website and your mobile app.
Challenge Alerts
Show alerts when you receive a challenge
- ✅ Everyone
- ⏹️ Friends Only

Yes that all seems to match my own settings. I know it sounds silly, but maybe try toggling your "Allow challenge" setting to "Nobody" for an hour and then revert back to "Everyone" ? Not a guaranteed fix but it may help?

I can't send you anymore challenge requests for a little while (there's a cooldown after 3~5 apparently) but will try again later. :]

Probably it's because i have just disabled all settings related to it.
I will re-enable them after a hour.

It gives you a different notification depending on whether you've sent too many challenges or can't send them at all, so there's that, I guess. We'll figure it out eventually, I am sure!

Well, we tested it again.
I still don't receive any challenge notification.
I heard a board button should appear at top of screen (next to Settings button ⚙️), but it doesn't appear for me.
Nor i get any other kind of notification about it.
But i get notification for DMs or forum posts.
I only don't receive challenge notifications... that's odd.
Whenever my friends request challenge, no notification or anything happens for me.
I have reviewed the settings multiple times, and ensured that the options related to it are all ticked, but still nothing.
Currently, only i can initiate a challenge, so they should request me via DM first, so we can play a game.