Break up

After your connection stabilizes, say
A. that you're back
Sorry, we got disconnected for a second, but I seem to be back now.

B. that you missed sth
Sorry, you broke up there for a second. Would you mind repeating the last part?

C.that it might happen again
Sorry, the connection on my side seems unusually unstable today. I apologize in advance if I disappear for a moment.