Using crab's ability

[lameduck]

Hi, newcomer to this game I did not succeed in using the crab's ability.
I can select the card I want to move, then two red arrows appear but then no matter where I try to move the card nothing happens (N.B. I am playing on phone only).
Any useful information for me as to what I should do ?
Thank you for your help.

[thoun]

Click the arrow to move the card

[lameduck]

Many thanks Thoun. Not very easy to use on a phone screen but it's working correctly using the zoom.