I can preview but can't save scan with Epson L220

I had the same problem using different scanner hardware (XP-960) using imagescan. What I did to solve this problem was to force the English language before running imagescan.

Go to a terminal by pressing Ctrl+Alt+T and type:

LC_ALL=en_US.utf8 
/usr/bin/imagescan

Source

The solution for Ubuntu 18.04 LTS and Ubuntu 20.04 LTS is not to set LC_ALL=en_US.utf8, as suggested in another answer, but LANG=en_US.utf8:

$ LANG=en_US.utf8
$ /usr/bin/imagescan

Note that this means that you will run imagescan from the terminal and NOT from the icon provided by the application.

You can also run the above in one line as:

LANG=en_US.utf8 /usr/bin/imagescan