Keged beer has gone flat

[4nabas]

I have a Magic Hat#9 that has been keged and have been drinking for a couple of weeks now. It has plenty of head, but now tastes flat. Any idea as to what has happened? Thanks

 

[loucurr]

I had this happen about two months ago and was able to attribute it to a leak in my keg cover. Tried to recarb but like yours always seemed flat after that.

 

[Cpt_Kirks]

Oxygen leaked in, maybe? Does it have a kind of "wet cardboard" taste?

 

[4nabas]

yeah, I found my regulator leaking at the tank. I guess that the gas leaked out and oxygen got in. It's a shame, it was a pretty good beer.