When I go to the website solo.ckpool.org, and I try to look up my mining history by entering my BTC address to
https://solo.ckpool.org/usersI get a page not found error.
Is ckpool.org really operational?
The pool is working fine, so it's something on your end.
Some things to check:
Miner Software: Make sure that your miner is actually mining properly. Do you see a hashrate number being displayed in the miner software/dashboard?
Hashrate: Are you providing a very small hashrate?, even at 300GH/s (one Compac F) the summary should appear immediately. If you're pointing a very old miner, or a non-asic device, then it will take forever to appear and it will display the error in the meantime.
URL: Of course, any mistake in the URL would generate that error. Double check that you're using the same BTC address you used in the miner.