Request for Template Contributor Account Approval as an Established Agency

You should network with Adobe's Partner Agencies to find out how they received invitations.  

Everything you need to get started can be found on this page. 

https://helpx.adobe.com/stock/contributor/help/design-template-requirements.html

Also familiarize yourself with Template Specifications & Guidelines below.

https://new.express.adobe.com/webpage/7ZycfV6RbQilz?

Hope that helps. And best of luck.

Could you please explain why our agency is not allowed to submit templates even though we are a professional, well-established team?

By @Minily

I do not speak for Adobe, but Adobe made it clear, that contributing templates is on invitation only, and that there are currently no invitations being send out. Adobe is free to choose it's suppliers, and when they decide, that they do not have the manpower to check those assets, they may well decide that they do not want more contributors in this field. Contributing is a privilege not a right, as Adobe is master in their own house. 

I suggest, that if you are such a big team, that you set up your own facility to market templates to the world. 

BTW: you did start off badly, by posting to the wrong forum. This is not exactly proof that they are familiar with Adobe's practices.

BTW2: Please note that if you "request" something, this is a very strict and very impolite way of phrasing it. I would have replaced "request for" with "please allow us to be". That is much more polite.

You are not addressing Adobe directly in this forum and will receive no reply from an Adobe rep here. I don't know how Adobe identifies Contributor accounts worthy of supplying templates.

What we know is that in order to submit templates, you need to be invited. How one goes about getting invited is unknown. Maybe by way of attending Adobe events and networking? Just a guess. And you are not addressing Adobe here, but contributors.