May I request you please confirm if you are using a brand new developer org for validating the challenge?
If you are using a brand new developer org then please double check that your org doesn't have a namespace enabled.If that doesn't help please give a try by restarting the batch
Still, if the problem persists log out of all accounts and log in once again in a different browser by clearing the cache and cookies which should probably do the trick.
Sorry for this issue you are encountering.
May I request you please confirm if you are using a brand new developer org for validating the challenge?
If you are using a brand new developer org then please double check that your org doesn't have a namespace enabled.If that doesn't help please give a try by restarting the batch
Still, if the problem persists log out of all accounts and log in once again in a different browser by clearing the cache and cookies which should probably do the trick.
Please let us know if this helps.
Mark this as solved if it's resolved.
Thanks,
Nagendra