Learn Spanish (Latin America): Este es un error importante, vuelve a intentarlo.

In Spanish, you often use the verb volver (which literally means "to return") plus the preposition a and an infinitive verb to say you are doing something "again." So, volver a intentar means "to try again." Here, it is conjugated as vuelve to give a command.

Why is lo attached to the end of intentar?

The pronoun lo means "it." When a verb is in the infinitive (unconjugated) form, like intentar, object pronouns must be attached directly to the end of it. This combines them into a single word: intentarlo (to try it).

Who is being told to "try again" with the command vuelve?

This is an informal command directed at "you" (tú). To tell someone to do something informally, Spanish uses the same verb form as the normal él/ella/usted present tense. If it were formal (usted), it would be vuelva a intentarlo.

Why does the sentence use Este instead of Esto?

Este is the masculine word for "this." It is used here because it refers specifically to un error (a mistake), which is a masculine noun. You would use the neutral esto if you were pointing at something unknown or referring to a general situation rather than a specific noun.