I have been working on sharepoint recently. I have created a site collection for my testing purpose, in which I have to upload documents in a library. I used REST API and CSOM to upload the documents and it's working fine.
Now the same code I have been using on another site collection which one of collegue have created, where I have full control, but every time I tried to upload the document I am getting an error of "Access Denied. You do not have permission to perform this action." I tried to use POSTMAN to upload the document by passing Bearer access token, still same 403 error. I used CSOM code to check if I can access the site or not, but I can access the site and print its list names or library or title name and all. Can anyone please help me for this scenario, I'm all lost.