A template with that name already exists in this language. Pick a different name.
Meta needs every template in your WhatsApp Business Account to have its own name and language pair. A template with this name already exists in the language you picked, so Meta would refuse a second one. Avox suggests a free name, such as the same name ending in _2.
Click the suggested name, or type a different one.
Or pick another language - the same name can exist once per language.
Or delete the old template from its page first if you no longer need it.
Still stuck? Send AVX-3400 to hello@theavoxai.com along with what you were doing when it happened.