Which sutta? The Buddha says monks missing out on pleasures of lay life and pleasures of holy life Which pali sutta is this?
I think it's in MN somewhere.
The Buddha says monks missing out on pleasures of lay life and the pleasures of holy life.
The idea being that their practice is such that they're not getting jhana (pleasures of holy life), and they're deprived of the pleasures of the lay life (food, sex, etc), so they're just suffering.
You're probably thinking about Dhammapada 155-156 (translated by Ven. Thanissaro):

Neither living the chaste life
nor gaining wealth in their youth,
they waste away like old herons
in a dried-up lake
depleted of fish.
Neither living the chaste life
nor gaining wealth in their youth,
they lie around,
misfired from the bow,
sighing over old times.

Alternative translation here by Ven. Buddharakkhita:


Those who in youth have not led the holy life, or have failed to acquire wealth, languish like old cranes in the pond without fish.

Those who in youth have not lead the holy life, or have failed to acquire wealth, lie sighing over the past, like worn out arrows (shot
from) a bow.



Additional references include:

Iti 91: so by such a simile do I speak about this person: he has missed out on the enjoyments of a householder, yet he does not fulfil the purpose of recluseship.
SN22.80:7.4: I say that person is just like this. They’ve missed out on the pleasures of the lay life, and haven’t fulfilled the goal of the ascetic life.