Pens Stopped Working on the Surface Hub

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We have a hub that one pen stopped working, so we used the other pen.  Now that pen has stopped working too.  We brought a pen from another hub and it works fine.  So it is definitely the pen….  Any suggestions?

[#2]

Jump on the Surface Hub website and log a warranty fault for the pens.
Also, is there any chance people are putting the pens in the wrong way and they're going flat?

[#3]

+1 for upside down pens not being charged, my users do that all the time and it drives me nuts.

[#4]

As per the other replies, check that it has actually charged (users always put them in upside down), otherwise raise a warranty call here: https://support.microsoft.com/en-gb/help/4037644/surface-contact-surface-warranty-and-software-suppo...