Additional features, settings, or issues not covered by specific Microsoft Teams categories
Hello jmhoCU,
Ok, let's try this:
First, a little explanation about SharePoint and Teams, when you create a team in Microsoft Teams, it will create a SharePoint site with same name, each channel on the team will create a folder with same name in the SharePoint site.
So, you have to verify if the main library of the SharePoint site has an special conditions like required columns, the check in/out feature activated or the Approval feature, this features could create the conflict that you are facing.
Also, you have to verify if you have the right permission, basically you need to have an "Edit" permission level on the SharePoint library to create a new file there.
By other hand, when you click in "Open in Excel" button or the "Sync all responses to a new workbook" from the form to see all responses, immediately, the SharePoint library it will create an Excel file on the channel folder, I mean, if you have created the form in the "General" channel, the Excel file will be in General folder of the SharePoint library.