Thanks for the reply. I checked and the bit depth was set at 32bit albeit at 44.1kHz. Normally my CD burner is fine with converting this to 16bit but I had to reinstall all my s/w recently. So it's possible the latest version doesn't accept 32bit . I'll try to remember to export at 16bit from now on.
I had a problem exporting to WAV using the new faster feature. The format wasn't compatible with copying to CD despite being playable from all media players. Tried to copy tracks using two different s/w which have worked fine in the past. There were two tracks which did copy correctly which I had created on Bandlab. Is this a known bug?