I tried finish trailhead challange and I did prework and working correctly when I did last chalange and want check this then I got this strange error. I can't find any ifnroamtion on this error. I also create new Playground but it the same problem. 

"Challenge not yet complete in Cunning Panda Playground
We can't check your work because something in your org prevents creating and updating account and opportunity records. Check the settings and configuration of your org. Make sure you can create and update account and opportunity records. Then click Check Challenge again."

https://trailhead.salesforce.com/content/learn/modules/custom_metadata_types_dec/cmt_formulas

 

 

How to solve This Error...

I'm trying to complete the chatter section on Trailhead, and I'm getting the error "Challenge Not yet complete... here's what's wrong: 
No feed post was found that linked to the Trailhead URL.", and this doesn't make sense because I clearly posted the URL multiple times.

The criteria: Using the standard poll and link Chatter actions, create two posts to engage with the Chatter user community.
Create a poll post. Ask your users to rate their experience with Chatter and ask for feedback in comments.
Create a link post. Share a link with other users to http://developer.salesforce.com/trailhead - the best learning tool for Salesforce out there!