Hey! The Epigraphic Database Heidelberg only records Latin or bi/trilingual inscriptions that include Latin texts, so you'll only find those when you search via their form. And while they do have all inscriptions from the province of Achaia published so far, if you find none for Tanagra that probably means there have been none published so far. The ones found via Clauss-Slaby (which theoretically only collects Latin as well, but has some Greek) only contain Greek text (which is what the 'GR' stands for). I find their interface not very user-friendly, but that's beside the point.

If you need to look for inscriptions from Greek-speaking territories that are not primarily Latin, even during Roman times, your go-to sources are the Inscriptiones Graecae as a corpus and the Supplentum Epigraphicum Graecum, which systematically collects newly found inscriptions in annual volumes, similar to the Année épigraphique for Latin inscriptions.

You can find some IG volumes online at the Berlin-Brandenburg-Academy of Sciences homepage:

http://telota.bbaw.de/ig/editionindex.html

But I don't think Boeotia (which is in IG VII) is included. SEG has an online database as well, but it seems hard to access for people not affiliated with Hamburg university for some reason. Or I can't get it to work from my home network, maybe it works for you from a campus network: https://www.sub.uni-hamburg.de/recherche/datenbank-informationssystem/detail/datenbank/9351.html But for Greek Inscriptions in general, you can try the PHI-search:

https://epigraphy.packhum.org/allregions

You should be able to find some from Tanagra there. Good Luck!