The VHS players have, by design , a less stable synchronization signal output. To compensate that the tuners and the IF stages in the older tv's were designed with a special setting on the sync circuit that allowed them to react a lot faster to follow the signal. Newer tv's and equipment like your AV/tuner stick still have it but it needs to be manually activated, otherwise when the signal coming from the VHS is fed into it it's deemed corrupted and ignored.
To do that use the Composite input and configure it in the Channel Manager: select the image format (probably NTSC) and select the VCR in the Description box. If even after that you still don't get it then the stick is not sensitive enough to compensate the fluctuations in the signal. That you can't fix, you will need another one - preferably an older, second-hand one model.

It should be on input 1 2 or 3.