Perhaps I don't understand the autofocus system, I am using Canon EOS R6. So I tap my subjects eye on the LCD screen and then the camera shows the autofocus square over their eye and adjusts focus. Now as they move around, the autofocus box tracks their movement but it never makes any adjustments to the focus as they move. Correct me if I am wrong, but isn't the idea that once it finds the eye, it should re-adjust focus automatically as the subject moves closer or farther from the camera?
You could try resetting the camera back to its Factory Default settings. The needs to be in SERVO AF mode.
As mentioned, the camera must be in servo mode or as it's called on the R cameras "Continous AF".
The factory default AF mode setting (AF Menu->page-1->Line-5 -> "Continous AF") is [Disable]. Auto focus will then only happen when the shutter is half-pressed.
The other option [Enable] will provide continous focussing, but with a reduction in the total number of shots available since the lens focus motor is running all the time. It's generally best to turn off Continous AF when you don't actually need it to save your battery run time and wear and tear on the lens.
2/07/2023: New product announcements!EOS R8 EOS R50RF-S55-210mm F5-7.1 IS STMRF24-50mm F4.5-6.3 IS STMRF15-30mm F4.5-6.3 IS STM