If you upload an Excel file that is protected with a password, Sheetgo shows an alert and does not import the file. Sheetgo cannot open a file that asks for a password before its contents can be read.
Remove the protection and upload again
Open the file in Excel and enter the password.
Remove the password. In most versions this sits under File, then Info, then Protect Workbook, then Encrypt with Password: clear the password box and confirm. The exact menu differs between Excel versions and between Windows and Mac.
Save the file.
Upload the file to Sheetgo again.
A file that opens in Excel without asking for a password imports normally.
Protection that only locks cells or sheets for editing does not stop an import. The alert appears when a password is needed to open the file at all.