Actually the experts have toured all the nuclear facilities in Iran. Read the IAEA
report for details. The IAEA has inspected the facilities to the extent that is has verified the non diversion of declared fissionable materials. The remaining issues on the table deal with past intentions and studies carried out in Iran. The IAEA has reached an agreement with Iran on how to resolve these issues, but the USA and France are blocking this at the UN level.
It should be noted that the Non-proliferation treaty affirms the
inalienable right of nations to the use of nuclear research and other peaceful uses, Article IV.1 emphasis mine:
So the UN resolution which demands the cessation of enrichment has absolutely no grounding inside the NPT, by the strict wording of the above article.