Sorry, you’re wrong; they’re right.
The sentence reads: “...the hours-long interruption of its internet, video and voice services, was caused two separate...”
The subject (”interruption”) is singular, so the verb (”was”) must also be singular.
Correct. The interruption ... was caused ...
I don’t know here you all went to school, but it should read:
“was caused by two separate”
With “by” being the missing word.
It is a glaring mistake that stops the reader dead.
How you can read this:
“was caused two separate “
How can you not see anything wrong with that?