I just received this email from Belize Tranfers. Just in case it affects anybody traveling via Cancun:

"Right now Belizean taxis are not allowed to pick up at the Bus terminal.
So we are meeting our clients at the Restaurant right infront of the New Market in Chetumal.

When you arrive in Chetumal bus depot you take a mexican cab and ask them
to take you at the Mercado Nuevo right where the Belize bus park. This is
only a couple of minutes away from the terminal."