Hello Philippe! It seems like Linked Selection might have been turned off, which would explain why you’re only selecting the video or audio instead of both together. Try pressing Shift + L to toggle it back on, or check for the icon in the middle of the ones that are on the upper left part of the sequence panel, if it’s not highlighted, click it to reactivate it.
If that doesn’t solve it, the clips might have been unlinked manually. In that case, just select both the video and audio, right-click, and choose “Link” to reconnect them. That should get things back to normal!
Best,
Ivan Eldredge G.