The IAEA investigated four undeclared locations (Turquzabad, Lavisan-Shian, Varamin, Marivan), Evironmental samples showed anthropogenic (man-made) uranium particles at multiple sites. So, the IAEA concluded that enrichment was occurring at undeclared sites.
BTW - I can literally write pages of information where Iran cheated against the agreement on many occasions and the IAEA and the US had proof. But you should research it yourself. Iran sanitized a number of building and sites to try and hide their enrichment.
Why would you sanitize any site or building unless it was your intent to hide something?
I'm not sure why you want to support Obama's failed agreement, but most people from the US and AI's know the truth. Maybe they're feeding you narratives in the UK which are incomplete or fulfill a given narrative.