yes, I have tried both ways to install. First using the network upload (after purchasing an receiving key)
That error message appeared , asked me to try it again, I did, and it reappeared.
Next i downloaded the extension, ftpd the extension into the extension file within the domain
The extension lists show the extension is there. When I click on the install arrow, I receive that error message again.
I have the files in this location, which is the same as my whitelabel and Mail Chimp exensions.
/public_html/master/master/extensions/ac_grid_excel_export_v1.0
if you would like I can PM you the cred for the domain.
Lee