I now see that my Trailhead Playground is acting up similar to others...and I thought it was just user error!
I too am experiencing the same messages:
"Please hold while our robots build your Trailhead Playground. This may take a few minutes" and
"Our robots are still working..." while trying to complete Module Trailhead Playground Management-2nd part Create a Trailhead Playground.
I am also unable to complete Module: Accounts & Contacts-2nd part Understand Account & Contact Relationships.
Actually I'm unable to complete any Trailhead that has a challenge because my Playgrounds don't work, are competing with each other or over-riding each other.
I have a couple of My Trailhead Playgrounds and also a Developer Edition Playground which I created under an email not connected to my SalesForce account. I am hoping there is a way to delete or fix the DE Playground. I'm honestly not sure why I even ended up in the Developer areas of SF since I am not at all a developer...
I really think that if I could just wipe the Developer area clean of my interactions, maybe Trailhead would be of some use for me as an admin. Can someone help me find where to submit this as a case to a support team that feels it is part of their responsibilities. I talked to a SFguy at the Trailhead learning center at the latest SalesForce Event held in Minneapolis (Fun!), and he said he had a similar experience and support had to go in and make some changes...hoping someone can help here...I really need this to be working correctly.
 

I now see that my Trailhead Playground is acting up similar to others...and I thought it was just user error!
I too am experiencing the same messages:
"Please hold while our robots build your Trailhead Playground. This may take a few minutes" and
"Our robots are still working..." while trying to complete Module Trailhead Playground Management-2nd part Create a Trailhead Playground.
I am also unable to complete Module: Accounts & Contacts-2nd part Understand Account & Contact Relationships.
Actually I'm unable to complete any Trailhead that has a challenge because my Playgrounds don't work, are competing with each other or over-riding each other.
I have a couple of My Trailhead Playgrounds and also a Developer Edition Playground which I created under an email not connected to my SalesForce account. I am hoping there is a way to delete or fix the DE Playground. I'm honestly not sure why I even ended up in the Developer areas of SF since I am not at all a developer...
I really think that if I could just wipe the Developer area clean of my interactions, maybe Trailhead would be of some use for me as an admin. Can someone help me find where to submit this as a case to a support team that feels it is part of their responsibilities. I talked to a SFguy at the Trailhead learning center at the latest SalesForce Event held in Minneapolis (Fun!), and he said he had a similar experience and support had to go in and make some changes...hoping someone can help here...I really need this to be working correctly.
 

On the Hands-On Challenge for Create a Trailhead Playground, it has not created the playground. I let ht run for an hour this am. 
After which time I closed the window. came back about 5 hours latter and it is still in the same spot "Our Robots are still working..."
HELP!!!!

This is so frustrating!!!