can't create new folder in Salesforce

I tried to create new  Box folder in Salesforce recorde but an error occured like below.

"Sorry, there was an issue with processing this request.
Unable to create a box folder for this record: Unable to create folder for record id a07F400000QQtPoIAL - Details: Unable to call Box using default credentials (this could be in a trigger or constructor, or after a DML statement) Your connection to Box is no longer valid. Please contact your administrator."

I think that Box and Salesforce are connected because I am able to view the Box folder created before  from the Box file Object.

Also I confirmed that Object FolderId match the box folder path value.

Please tell me how to resolve this error.