@helpmelearn (Helpmelearn) posted a new topic, subject "Ionic 3 prod build errors". It read:

   My company forced us to upgrade Mac and test iphone 7 to 13.5.1.
    
    Finally able to build app (as normal I start fresh with installing node modals and remove and add ios 5.1).  
    Now getting problems testing app on said iphone.  
    I can get the app to work if I don't **do a prod build**.  
    Everything being the same, just one build using --prod another not.
    
    No build errors. Open in Xcode, no build errors. Pushed build to phone. Get errors in log.  
    See something similar as its loading.
    
    On our login screen just tapping into a text field get this error.
    
    **ERROR: ERROR Error: StaticInjectorError[l]:**
    
    **StaticInjectorError[l]:**
    
    **NullInjectorError: No provider for l!**
    
    Every time a key is pressed. This is the cause of something else.
    
    Strange thing is push same build to iphone 8 simulator running 13.5 no errors.  
    Honestly I'm not sure what else to do.
    
    Any idea why a prod build now on 13.5.1 would cause this?
    [code] 
        Cordova CLI       : 8.0.0   
        Cordova Platforms : android 8.1.0, browser 5.0.4, ios 5.1.1
        
    [/code]

Then @helpmelearn (Helpmelearn) said

    This was related to a firewall issue. Our company has witched VPN companies and really didn't have a good plan on how this would work with mobile phones accessing internal sites. Causes websites to not response and crash in code.

To which @webteambel (Webteambel) replied

    helpmelearn:
    
    > prod
    
    Try to test the application with test flight
    
    1- Run a build try : ionic cordova run ios – --buildFlag="-UseModernBuildSystem=0"  
    2- Open xcode and generate an archive to your app using a valid profile (manual manage signing)  
    3- upload ipa generate via xcode to appstoreconnect  
    4- make sure you have testflight on your iphone  
    5- install app via store and try to test


{'source': 'discourse', 'url': 'https://forum.ionicframework.com/t/ionic-3-prod-build-errors/192921', 'title': 'Ionic 3 prod build errors', 'views': 316, 'has_accepted_answer': False, 'word_count': 433, 'like_count': 0, 'reply_count': 1, 'participant_count': 2, 'posts': 3, 'tags': '', 'author': '@helpmelearn (Helpmelearn)', 'participants': '@helpmelearn (Helpmelearn), @webteambel (Webteambel)', 'image_url': [None], 'created_at': '2020-07-16T20:02:08.458Z', 'last_posted_at': '2020-07-28T14:40:32.597Z'}