The multiple Google accounts login issue
The upload error can be caused when you are logged in with two or multiple google accounts. This is a known Google accounts bug that they won’t fix.
When you are logged in with multiple Google accounts add-ons cannot work properly.
To workaround this issue/limitation, you can add different profiles to your Chrome browser with the email address of your FileDrop license and switch to the profile to use the add-on only with that account.
Instructions
Please make sure you are logged in with only one Google account or switch the profile in your browser as above.
Step 1
Click on the profile icon and click the Sign out of all accounts.
Step 2
Now that you are logged out off all accounts login back only with the Google account where FileDrop is installed.
Language is other than English and has non latin characters
Due to the way formulas work with FileDrop you might encounter errors if you are using Sheets in a language that doesn’t have support for latin characters, ex. Turkish.
Please change the language of your Google Account and the settings of your Docs from the File->Settings link.
After making the changes, please refresh the document page and start FileDrop again.