I've been back in touch with Teac phone support and they have upgraded my remote over the phone - I still have no idea why the sound files from the internet won't load....

But, they told me I still can't control DVDs (I have a Pioneer DV-355). So I asked them to load the Laser Disk codes for Pioneer - which they did successfully.
My remote now accepts VCR device codes 571, 525, 548, 632 & 638). But none of them will control my DVD player :-(

Maybe I'm stuck with a remote that is obsolete. And to quote the manual "as you buy new products in the future, the ONE FOR ALL 6 will never become obsolete".