Are you in a protected region that you are not added to?

Is it outside the edge of ECC?

Was there server lag then (have you tried after a fresh restart)?

What tool were you using?

There is not enough information in this thread for anyone to help you find an answer... Please provide for information (there is a format in the sticky of this section to help sort out thoughts).

 

Probably a mixture of lag and server protections for breaking things too fast, etc. You would need to find others with the same pickaxe to really test.