@steve_flogeras
Thanks, seems to be the same file I used and I still have issues replicating your error. The StartsWith functions uses a different structure, try this
//SortByColumns(Search([@FlooringEstimates], TextSearchBox1.Text, "Category","Name","Overview"), "Category", If(SortDescending1, SortOrder.Descending, SortOrder.Ascending))
Filter( FlooringEstimates, IsBlank(TextSearchBox1.Text) || StartsWith( Name, TextSearchBox1.Text) || StartsWith( Category, TextSearchBox1.Text))
Also, are you using the 'OneDrive for Business' connector. There is a different OneDrive connector which may/may not cause issues? I cannot check this, sorry, ie

- connectors drive PowerApps so this needs to be correct.
The linked article says this at the top
Note
Power Apps requires either a Microsoft 365 license or a free trial. Learn more about your licensing options. Microsoft products include Microsoft Power Apps and Power Automate.
So, you need one of these to make this work.
There may also be something going on at your Tenant / Environment level? This just worked for me on my work account but you are having issues which suggests this maybe the case.
Maybe a MS employee on the forums knows more?
@v-bofeng-msft @v-xiaochen-msft