Beta 8 - Audio no longer working for me?

I have upgraded today from beta 5 studio to Beta 8 (2nd version). This was done as an uninstall, then install beta 8. I waited until i had finished and delivered a
project. When i load the project now in beta 8, there is no audio from the timelines or indeed in any section, inc fairlight. However, when i render out a part from deliver, the audio is there on the rendered clip! All other audio outside of davinci works fine, so not a system setting, and i have restarted everything. There is also no indication of sound on the mixer... I'm bemused. Presume i'll have to roll back, maybe to 7 first. Any suggestions before i roll back would be appreciated.

[Peter Chamberlain]

Please check your audio speaker monitor settings in preferences

Thanks Peter, that had changed back to system in the speaker setup for some reason. All seems to be working now. Appreciate the input and all the improvements being made.