Try installing this on another computer : https://chrome.google.com/webstore/detail/chromebook-recovery-utili/jndclpdbaamdhonoechobihbbiimdgai
Use this program to turn a USB or SD Card into recovery media.
Press and Hold Esc and Refresh, then press power. Keep hold ESC and Refresh until a message pops up on the screen. The message should tell you to insert the recovery media. Do so and follow the instructions from there.
Please note. This method will erase all your data, so if you need to recover your data you might want to try another method.