script to copy files from on premise file server to SP ONLINE

I have a script that I found in many forms online that I re-tooled to work in my environment.

The purpose of the script is to copy files from local File Server to a Library on my SharePoint Online.

I have it working to the site I want it to go to as long as the site's "Members Group" has Write Access to the sub directory. in this scenario, I need to limit access to this library and don't want the Sites "Members Group" to have access.

when I remove the "Members Group" and add explicit permissions for the Licensed O365 User that executes the upload, I get these errors:

You cannot call a method on a null-valued expression.
At C:\TESTMove_file.ps1:70 char:5
+     $FileUploaded = $FolderToUpload.Files.Add($FileCreationInfo)
+     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

Cannot find an overload for "Load" and the argument count: "1".
At C:\TESTMove_file.ps1:73 char:2
+     $Context.Load($FileUploaded)
+     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [], MethodException
    + FullyQualifiedErrorId : MethodCountCouldNotFindBest

Exception calling "ExecuteQuery" with "0" argument(s): "The remote server returned an
error: (401) Unauthorized."
At C:\TESTMove_file.ps1:74 char:5
+     $Context.ExecuteQuery()
+     ~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
    + FullyQualifiedErrorId : WebException

I haven't been able to find a reason this wouldn't work? Please advise.

thanks