There is an incompatibility with mod calamity: community remix.
You can excavate, but only if a helper from a community remix is on the screen and you don't click on the message from him. If you click on the message, he will disappear, and in that state, you can't excavate. If you try, it will give you the ore that you are trying to excavate, but the block won't disappear. However, if you go far away from that place and return, it will eventually excavate that ore.