Opening, sharing, and managing OneDrive-stored documents directly within Teams
Hi Salley22, I am Juliet and It's my pleasure to help you today.
How are you? I hope you are doing good.
I know how frustrating this may be for you but I'll do my very best to help you :)
I would like to know if it's a client related issue or not, you can check whether the attachments file can be upload successfully in https://teams.microsoft.com/ or not. If web-site works functioning, it should be a client related-issue.