When a Private Teams gets Created, If add another user as owner of the Team Group upon creation, this user will not have the access to see Files section and it returns error "You Don't have access to these files"
Four work arounds:
1. Change User from Owner to Member then user immediately have access to files
2. Change Team Group From Private to Public Group, all users in Team instantly have access to files
3. Go to SharePoint - Permission settings - Advanced Settings manually add a user in Member or Owner Group, then these users will have access
4. Do Nothing but wait for 3+ hours, the access for files tab will resolve by itself
In fact none of above are ideal solution, what really makes angry is Microsoft's support:
1. I first lodged a Ticket to MS Teams Support team, they remote on to my PC and watched this issue happen and saw i did the work arounds, then he told me eveything from Teams side looked perfectly normal and refereed my case to some one in MS sharePoint Team
2. Then i Had SharePoint Support engineer remote onto my PC i managed to re produce the issue, then he showed me how to just add users in sharepoint owner group blablabla and told me sharepoint works perfectly ........i told him you can not expect users to do all those work arounds when they are in a hurry trying to create team sharing files, people will just simply say MS Teams is Sh*t and dont want to use it any more after all those frustration. The Engineer tried and actually managed to reproduce the issue with his INTERNAL MS TEAMS CLIENT, after the sharepoint engineer claimed that he collected and captured enough data, he transfered me back to MS Teams Team.
3. Then i had this another MS Teams Support engineer emailing me asking for information i have been telling their previous engineers for two times, (yea, Microsoft develops Collaboration tools but seems their internal teams cannot collaborate ). This engineer told me he tried to call me multiple times but i was waiting for his phone call the whole morning but i didn't get any phone call at ALL
4. Now just keep on waiting for Microsoft to get back to me again, thanks Microsoft for Kicking the Ball around.