I cannot use 4k on my 4k Screen?
Have you installed the HooToo shuttle firmware update for MacBooks? If not, you can download this directly from here.

I would download/install the firmware update first to see if that resolves your problem. This eliminates the possibility that it's a firmware issue with the HooToo hub (otherwise you could spend hours troubleshooting other causes for absolutely no benefit).

If you still have problems after installing the update, please comment below to let me know.