Can not search out an existed mail list from office 365

We are building sharepoint list with PowerApps, need search user/group from office 365, 

so we changed the input text form as User/Group in SP list. 
However, we found some of Mail Groups are failed to search out from the box, which are confirmed in office 365 outlook.
Some mail group can be searched out but some can not.

Changed to PowerApps to try the office 365 user connector, same result.

So, we are confused is this mail group setting problem, or office 365 user api limit?