stand someone up
phrasal verb

- to intentionally fail to meet someone when you said you would, especially someone you were starting to have a romantic relationship with

(Cambridge Advanced Learner’s Dictionary)

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WORD ORIGIN

The Online Etymology Dictionary says this phrase was first recorded around the turn of the 20th century. Exactly how it came about is unknown. Perhaps it derives from the image of sitting around, waiting to meet someone, and then standing up to leave after realising that the person has no intention of coming. It may also originate from the idea of standing around (as opposed to sitting) for a long time while waiting to meet someone.

In either case, such people are referred to as "no shows" (in addition to other more colourful expressions). This comes from the expression "to show up", meaning to arrive for a meeting. Although the Cambridge Dictionary emphasises the use of this phrase in romantic relationships, it’s perfectly acceptable to apply it in the business world.

An alternative is the American English phrase "to blow someone off" (We agreed to meet for dinner, but then he blew me off!). WARNING: Don’t say this in the UK where it could have a completely different (s-xual, erot-c) meaning!

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SMUGGLE OWAD into a conversation
say something like:

"This is the third time that we arranged to meet,... and they STOOD US UP again!"