If a person who has ablution tries to urinate, pass gas, or pass stool yet nothing exits from their body, is their ablution still valid?

All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

If nothing comes out of him, then this does not affect the validity of his ablution, even if he intended to invalidate it by trying.

The Kuwaiti Encyclopedia of Fiqh reads, "The majority of the scholars held that the intention is one of the pillars of ablution, so if the person rejects the intention after having performed ablution in full, this rejection is of no effect."

Allah knows best.