Why r not download any application like as messenger, Facebook etc

Here are some possibilities:

'Your account has been disabled in the App Store and iTunes' https://support.apple.com/en-us/HT208856. This link says: "There might be a problem with the payment method that you have on file. When you see the message, don't try to edit any of your account information. Instead, contact Apple Support for help.”

Try using the Apple recommended support link above first. But, this site is down very often. Use the support options I give below if necessary.

You can also Get a call from Apple support to help solve your problem https://getsupport.apple.com/?caller=kbase&PGF=PGF63005&category_id=SC0245&symptom_id=23362

And you can use Apple Support Twitter https://twitter.com/AppleSupport

And, if necessary, go here to contact iTunes worldwide support via text or chat https://support.apple.com/choose-country-region/itunes After choosing your country, see the heading, Tell us how we can help.

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If you can’t download or update apps on your iPhone or other Apple device https://support.apple.com/en-us/HT207165

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If you can't connect to the App Store, iTunes Store, or other Apple services https://support.apple.com/en-us/HT201400. There have been quite a few Apple server connection problems lately. Among other things, in the above document, see Check Apple’s System Status page. You can check there to see if the needed server is available when you need to use one.

What happens when you try? Error message(s)? More information would help.