"Issues" are problems. To "require" something means that you need it. "Immediate" means right now or very soon. And "attention" means noticing and dealing with something. So the meaning of this phrase is "problems that someone needs to deal with quickly". In the example above, the writer wants people to call her if they have a problem or question that they need her to take care of quickly.
Use this phrase in formal e-mails and written business documents.
"Attention" is the most common thing that people require. Other words that often follow "require" are:
- require approval for something
- require treatment
- require assistance with something