I have been trying to download a app and I haven't been successful. It tells me to constant support each time. Every other app downloads with no problem.

Do as the message instructs, contact Apple Support at:

www.apple.com/support/itunes/ww/ --> https://support.apple.com/country-selector/itunes > select your country > Contact Support > Contact iTunes Store Support > Purchases, Billing & Redemption

or:

iTunes Customer Service Contact - https://www.apple.com/emea/support/itunes/contact.html

Might want to contact the developer directly if a link is available on the app's entry on the App Store. It could be transitioning from one version to the next or maybe not yet available in your country.