"There was a problem loading this world" for a world, can't load it at all.

How do you clear the mac address and what do you mean by persistent storage

There are multiple workarounds to follow; for instance clearing MAC address , and persistent storage!

You can also try to power cycle your console through which you turn off the console and remove the power cord; wait for 1 to 2 minutes before plugging it back in and turn on the console!

If this doesn't' fix the issue, I am afraid you might want to create a new world!

You can also reach out to minecraft to see if there is anything else that could be done!

Here is how:

Settings > Network Settings > Advanced Settings > Alternate Mac Address > Clear

Then select System > Settings > devices and streaming > blue ray > persistent storage > clear three times > restart console.

You will reset the console keeping the games and app. Nothing will be deleted.

I will talk to Mojang before I do that, I would prefer not to spend two days reinstalling all the games I have currently.