Hello Tianyi,
One more thing to try. In the WaveVision5 GUI, navigate to the "Registers" tab on the right side (shown below).
Toggle the Clock Selection to "External Clock" then back to "Internal Clock". There could potentially be a timing issue that is marginal in the FPGA code. If this solves the problem, then you will likely need to add some delay in the code to allow the clock to be properly and full programmed before advancing.