Are you dowsing when you do this?
It could be that you're not talking to your guides. I know when I'm talking to my guides now because I get a certain energetic 'signature' feeling from them when they show up - it's like one part love and one part familiarity. Did it feel like you were speaking to a guide?
The second possibility is that you're so attached to getting the right answers that your subconscious or ego is interfering. You can push that aside by relaxing and not placing expectations on yourself or the process.
You may also sometimes speak to guides who aren't your primary guide and that's OK. You will have one primary guide who's been with you since birth and a few more besides - they are all worth conversing with.