Does a land entering the battlefield tapped prevent you from tapping it immediately for mana?

When a permanent enters the battlefield tapped, it is placed on the battlefield in the tapped state (CR 110.6). A tapped permanent cannot be tapped again — you can only tap a permanent that is already untapped (CR 302.6 covers lands broadly, but the core rule is CR 701.21a: to tap a permanent, it must be untapped).

This means if a land enters the battlefield tapped — whether due to its own ability, an opponent's effect, or a replacement effect — you cannot immediately tap it for mana. You must wait until it becomes untapped, which normally happens during your next untap step (CR 502.1).

Note that this is distinct from 'summoning sickness,' which applies to creatures and the specific act of using a tap ability that requires the creature to have been under your control since the start of your turn (CR 302.6). For lands, there is no summoning sickness rule — instead, the simple physical state of being tapped prevents further tapping regardless of how long you've controlled it.

Example: You play Sunken Hollow, which enters the battlefield tapped unless you control two or more basic land types. If the condition isn't met, it enters tapped. You cannot tap it for blue or black mana this turn; you must wait until your next untap step.