Buying power is the dollar amount your broker will let you use to open new positions right now. It is not the same as your account value: open positions, pending orders and margin rules all reduce it.
Options often reserve buying power differently from stocks. Selling an option can tie up much more than the price you received, while buying an option usually uses the price you pay.
On CNKTID, every new copied trade checks your actual brokerage buying power at the moment the trade is requested, not a saved balance. If there isn't enough, the trade is skipped and you see why. Closing trades are never blocked by this check.