adobe illustrator - What does it mean when printers have told me my colour is not a Pantone colour, but in my file it is?

I've recently designed a cosmetic label for a client and I've given them the final file to have it printed at their designated printer companies.

But a few have them have come back and said that they can't print it because the colour isn't a Pantone when in fact, on my Illustrator file I clearly picked a Pantone colour because on my colour swatch, it says "Pantone 649U".

Does anyone know why they might be saying that? Is it just me or have I done my file wrongly?

I'm so positive that I've used a Pantone colour because the usual printer company I go to have managed to print it true to colour when I tested it but every time my client gets back to me about one of her printers, it's either the colour comes out so neon or it's a completely different colour or they just say they can't print it because it's "not a Pantone" colour.

If anyone could shed some light as to what I'm doing wrong, that would be great!