Is present perfect the most difficult?

Hello colleagues, In my class this week with low and high intermediate learners, we are focused on present perfect since this verb tense was featured in the article we are reading.  What have you found to be a good approach to teaching present perfect? What makes present perfect challenging? I'm wondering if teachers have resources they can recommend for teaching present perfect. Thanks for your thoughts and suggestions!

Cheers, Susan Finn Miller

Moderator, English Language Acquisition CoP