I had this problem for a bit. Sounds like you havent got the valve and tube inside the tyre properly as said up there. I found a tiny bit of grease inside the tyre by the valve helped it all pop into place easier.
@Conan started
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I had this problem for a bit. Sounds like you havent got the valve and tube inside the tyre properly as said up there. I found a tiny bit of grease inside the tyre by the valve helped it all pop into place easier.