Under the Developer option, I created an app but when I go to sandbox company connections, showing this error "You have no available connections right now." plz advise

It's great to see you here today, @aac123.

Let me route you to the best support who can help fix the error you received while connecting the app you created in QuickBooks Online (QBO).

We have a separate and dedicated forum that handles sandbox concerns for QBO. This is where developers and business people like you discuss programming and system issues. I'd suggest posting your question from there. This way, our developers can provide the appropriate fix for the sandbox connection error you encountered. Here's how:

1. Go to the Intuit Developer page.
2. Choose QuickBooks Online under What do you need help with?.
3. Click Ask a Question. 
4. Log into your existing Intuit Developer Account. 
5. Enter your concern.
6. Click Ask.

Also, you may want to utilize the helpful API topics on the Intuit Developer page. To do this, go to the API Docs & Tools menu, select QuickBooks Online, and choose Sandbox. 

You can count me in if there's anything else you need in managing your business's growth and transactions using QBO. I'm always ready to help. Take care, and have a great day, @aac123.