Sister is on Virgin Voyage cruise and hasn't been in contact. Is there often connectivity issues on ships?

My sister is on a Virgin Voyage cruise right now and she's typically quite good about checking in when she's traveling to let us know that she's safe. She also usually documents her travels fairly extensively.

She's been away since Sunday and hasn't reached out since before the cruise sailed. She hasn't been active on social media at all either. I just assumed that there's connectivity issues on the ship, but she travels with an iphone and an ipad and it seems like the ships do have good enough wifi capabilities to at least communicate via Facebook messenger? Should I be worried or is it typical for people on cruises to just enjoy the cruise and not reach out to friends and family?