Instead of looking up by name or phone number, is it possible to look up reviews by agency?

Reviews>>>>more searches>>>>search agencies.

I tried this and I put in searches for two well-known agencies and nothing comes up

Were you looking for reviews of agencies or reviews of escorts that work as a specific agency.

That's not an option. But it says to leave it blank to search all agencies of Virginia and when I do that nothing comes up not even one agency?

When suggesting using the email address I meant to put that in the search parameters in the Advanced Search in Reviews, not the Agency Review.  Of course if you don't know the agencies or their emails then not much help.

A couple of other suggestions.
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1. If you are searching "Virginia" (the Location, not the Provider name), there might be none BASED in VA. Some agencies are based elsewhere but take appointments, etc. outside of their base.  Depending on the agency, their website might have "location" tabs or "calendar" (who is where for the next week: "Alice Boston, Betty Boston, Carol Boston, Debbie DALLAS") tabs, etc..  
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2. Can you find at least ONE Provider profile you like in your area that is repped by an agency? IN THE PROFILE, click on the "phone number" hot link and you will get every Provider who shares / uses that number = the number of their agency.  Do the same thing for any hot linked (blue font) Agency and hot linked (blue font) for email. (Well, the email hot link might try to open your mail app so you have to cut and paste it as plain text into a separate Profile search.)  
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3. The DOWNSIDE to the above search suggestion would be touring K-girls. They might have 1 or 3 or 6 agency websites and phone numbers on their Profiles. Usually, those agencies are local only. When KG is in Boston, she's with Agency B. When KG goes to LA for a month or two, she is at Agency LA. Etc.. Agency LA will NOT be making appointments for KG when she is in Tysons.
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4. Search the VA - WV BUZZ board and in the (current) top 4 posts you will find Magnolia Secrets.  
https://www.theeroticreview.com/reviews/showAgency.asp?id=1604
City:  Washington DC
Other Cities Serviced: Miami, Washington D.C.
(Their TER Profile doesn't say VA or Tysons, and that's why you won't find them with a VA search alone.)
Although they are based in DC, they list several models in Tyson Corner.  
Scroll through a few more pages and you might find others.  
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Good luck.