Let's break it down:
* entonces: This means "then" or "so."
* Sean: This is the third-person plural form of the verb "ser," which means "to be."
* usted: This is the formal "you."
The issue is the combination of "Sean" and "usted." "Sean" is plural, while "usted" is singular.
Possible Correct Phrases:
* Entonces, sea usted: This translates to "Then, be you" or "Then, you be." This is a grammatically correct way to use the phrase, but it's not a common expression in everyday Spanish.
* Entonces, sea: This translates to "Then, be." This is a more natural way to express the idea.
* Entonces, usted sea: This translates to "Then, you be." This is also a correct way to express the idea.
Context is Key
To give you the most accurate translation, I need more context. What is the sentence trying to convey? What is the speaker trying to say?