Used to directly name the specific issue or obstacle that is preventing something from happening.
“The problem is, the printer keeps jamming right before we need to hand out the flyers.”
“The problem is that neither of us can drive on Saturday morning.”
This phrase is a strong signal in Listening Part 1 — it almost always precedes the core problem the two speakers need to solve together. Train yourself to note whatever comes immediately after 'the problem is,' since test questions frequently ask you to identify exactly that detail.
Synonyms: the issue is, the trouble is, what's wrong is