Tango seems unique in that many newcomers think that following a few lessons, either in a group or privately, is enough to get into social dancing.
The standard approach for beginning tango students is usually to attend classes for an arbitrary period, after which they jump straight into attending milongas.
It is not a surprise, then, that their typical first experience of social tango dancing is frustrating.
The length of such periods varies. Regardless, the result is often the same. Nothing seems to work; students can’t remember what they did in the classes, and nobody wants to dance with them.