If the Bitcoin Chrome Applicaton displays: "Sending failed: unable to validate transaction" when you try to send a Bitcoin Cash amount it can mean:
- that you do not use - and maybe did not download - the Bitcoin Cash application on your Ledger Nano S or Ledger Blue, from the Ledger Manager. Refer to this guide.
- or that you did use the Bitcoin Cash application, but something went wrong when synchronizing your information. If so, please reset the Bitcoin Chrome App : settings > tools > reset application data and try again