Action Blocks are failed like attempts. If a session (account / device / IP combination) is blocked, liking a post from the browser does not register the like on the Instagram server. Refreshing a post page after it was liked returns a non liked post.
Everliker detects such failed attempts and shows the "Failed to Like" message, stopping all tasks automatically. The action blocks are not (as far as we can see) caused by Everliker but by breaching the trust score limit.
Trust Score is a system used by Instagram to prevent like and follow functions abuse. Each action taken on a session causes that session trust score to change. Liking and following depletes the trust, while posting improves it. Trust score is only known to Instagram server and not client.
Fresh accounts and Devices have low trust scores. As the score reaches 0, certain actions are blocked automatically for that session. Trust score is restored over time. If a session was action blocked before, the overall account trust score decreases.
If you received a Failed to Like message on Everliker that means you were action blocked. You can test that by manually liking a post on Chrome and refreshing the page. The like will disappear from the page.
You can try to use the RECOVERY MODE feature found under GENERAL SETTINGS to reset your session and gradually build up the speed. If you are action blocked again during the recovery mode procedure, you can use the resulting speed as a reference and configure Everliker not to exceed that.
If you are repeatedly action blocked no matter the speed setting and Recovery Mode does not help that means your account trust score is too low to run automation and it might be better to refrain from using Everliker.