Pancakeswap telling me I have no BNB - what now?

PancakeSwapPancakeSwap
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self.pancakeswap1m ago
Hi, Although I've spent more than a year trading on Binance, I'm finding Pancakeswap totally mind-boggling. I'm hoping you can help me. I'm trying to buy a little-known coin that is apparently available through Pancakeswap. So, I have BNB in my TrustWallet and I tried taking steps to connecting my TrustWallet to Pancakeswap. This is proving totally impossible on desktop. Pancakeswap says "Provider Error. No provider was found" Ok, I think I managed to connect my TrustWallet mobile app to Pancakeswap (after 5 attempts) however when I'm on the SWAP screen trying to swap my BNB to CAKE, it tells me I have no BNB. Well, I definitely do have BNB in my TrustWallet. Two questions - how do I persuade Pancakeswap that I do have BNB? And, am I even on the right track trying to buy this smaller coin by swapping my BNB to CAKE? Or have I completely misunderstood the process? Thanks.