Is there an expression or idiom to express in an informal/funny way that it is a person's fault when something is not working?

Solution 1:

“I guess it just doesn’t like you”, would be how I would suggest phrasing it.

This matches the following OP criteria:

1) Focuses the issue as a personal issue of the person having trouble.

2) Humorous: The inanimate object has no particular sentiment.

i.e.

P1: “ Why does the vending machine always eat my dollar?!”

P2: “It just doesn’t like you.”

——

i.e.

P1: “Why does the printer never work for me?”

P2: “It just doesn’t like you.”

Solution 2:

I've always used the expression 'finger trouble' :

(Computer Science) computing trouble caused by operator error, such as striking the wrong key

Free Dictionary

It can be used (and I do use it) in other contexts than computing, for example driving, when it can be 'finger trouble' with steering/gear-stick or 'foot trouble' regarding pedals.

Even worse is the 'fat finger' error which, from time to time, afflicts the financial markets. This is when some guy somewhere on the globe inputs six trillion instead of six hundred and everything screeches to a halt.

Wikipedia