ios – iPad unable to confirm app (enterprise app)

Enterprise apps had been put in and verified very long time in the past in serveral iPads.

The apps can’t be opened all of the sudden in 1 iPad whereas no downside in different iPads.

It reveals “Unable to Confirm App” An web connection is required to confirm belief of the developer “iPhoone Distribution: XXXXX”

I am going to Settings > Normal > VPN & Machine Administration > Enterprise App
and click on “Confirm Apps”.

The apps nonetheless can’t be verified

Nevertheless, the iPad is connecting to Web
When visiting https://ppq.apple.com in internet browser, it shows “okay”

I attempted reinstalling apps,restart ipad…