Help ASAP, resmed s9 problem!

Help, my s9 is malfunctioning. I turned it on as usual and I could hear the air whooshing out . Then I got a message on the screen to shut lid . I opened and shut it until it clicks,but the message comes back each time. I can't use it and don't have a backup. Has anyone had this type of problem?
Thanks

Unplug it for a few seconds and try it again.

My fault, I took out the tub to clean today and noticed the silicone seal/gasket under the lid and took it off to wash (never realized it came off before). I had forgot to put it back on, all is fine now, thanks again.

Glad you figured it out.