Can't get suction using breast pump which has been fine up to now... help?

[VintageGardenia]

I'm using a Medela pump and it's been fine, I've been successfully expressing for my 10-week-old baby for the last month or so, this morning it's humming away but doesn't seem to be creating any suction, can anyone help?

I had this once, took me agest to figue out that the valve had come away (tiny white rubber bit)

When this happened to me i had overscrewed the top on and it had unscrewed iyswim

Aaaah gosh finally. Yes there's a very thin rubber ring and a bit of it had come away. Oh finally I can offload!!!

Thank you!