Unable to login to new TELUS TV+ app on iOS and iPadOS

Similar story here. TelusTV+ app worked fine for a few weeks; then last week I got a sign-in dialog when I launched it, and entered my myTelus username (e-mail address) and password, but it was not accepted. Force-quit app, restarted, same thing. Restarted iPhone - still not working. Tried logging out of TELUS in iOS TV Provider settings on my iPhone as suggested above by NightHawk. Then when I tried to sign back in on the iPhone, I got "Your TV provider service is temporarily unavailable. Please try again later" (tried multiple times). Then tried Other TV Provider Regions .../Canada, and got a Telus Sign-In username and password dialog, but get "Sig In Error". Good grief. Meanwhile, I can log in to myTelus in Safari on all devices, and using the myTelus app with my myTelus username and password. Wasted over an hour trying to fix it on my own (including removing and reinstalling the app from the App Store multiple times), and then 90 minutes earlier today with Telus tech support. Can't log in using the iOS app on an iPhone, iPad, Apple TV, or via Safari or Chrome to TelusTV+. Support tech tried unlinking and then re-linking our Optik TV account to myTelus and that did not fix it. He had me go through the steps with launching TelusTV+ in Safari on the Mac, and same thing on the iPad, and send him screenshots at each step. Said he will bump it up the chain and get back to me in 24-48 hours. Meanwhile, OptikTV seems to be working fine on all our TVs. Ridiculous - why can't Telus debug their apps properly before rolling them out to customers, and why is there nothing about this bug in the online help for TelusTV+ to save people all this wasted time?  I'm thinking of switching back to Shaw. 

UPDATE: I suspect there is an issue with handshaking between the iCloud Keychain and the TelusTV+ App. In my iCloud keychain (examined on a Mac laptop)  there are two "application password" items that appear to be updated when I first run the Telus TV+ app after installing it from the App Store, and also when updating the  iOS TV Provider settings on the iPhone. Both items belong to the com.apple.VideoSubscriberAccount access group. The first cannot be viewed or edited. However, the second ("TELUS") item is both displayed and editable after entering the keychain password. The contents of the password field, however, are an XML .plist that contains the quoted forms of the username and password in a long string list.  As an experiment, on the offchance that the app is writing to the password field of this keychain item incorrectly (after copying this text and saving it for restoration if needed later), I replaced the whole plist with the password in plain text, and saved it.

A minute or two later, the TelusTV+ app started working on the iPhone!  However, it still does not work in AppleTV or the iPad, even after signing out of Telus in the TV Provider + iOS settings and signing back in on these devices.

The password is written over by the XML plist on doing so, but the iPhone app continues to work.

I would have communicated this information directly to Telus technical support, but unlike most companies that provide a ticket that one can update with potentially useful information, there seems to be no way to do this with Telus (go figure!). I had also included the whole plist (with sensitive information replaced with placeholders) in this post, but got "Sorry, unable to complete the action you requested" when I hit "Reply". Perhaps somebody at Telus actually monitors this board, and will pass it along, in case it is helpful. 

Yep, more Telus hornswoggle - boggles the mind. Spoke to Telus rep #1 this am - told TelusTv+ was up and running with update completed (I still cannot log on to the app). During phone connection with Telus the line went dead. Phoned Telus back and spoke to Telus rep #2 who said that the app was still being 'tweaked' (ie. not working). Does Telus just have too many customers and are trying to get rid of the 'overload'?

Thank you Sugata - Telus owes you.  I adapted your steps and used on my Apple TV box and it worked. In Apple box, go to 'Settings' (toothed wheels), and under 'Apps' and a few other categories, remove any references to TelusTV+ that you can find - there's a few to either turn off, or completely remove, ie. 'User and Accounts' > Apple TV Accounts; 'Apps' > TV; 'Apps' > TelusTV+;  That way, once you re-install the TelusTV= app, it will recreate the app throughout the Apple system. It's a shame that Telus doesn't employ technical people who are as ingenious as many of their customers. 

Worked for me also on the iPad and Apple TV, thanks Sugat, great sleuthing!

Thank you for doing the work to figure this issue out, worked for me on my ipad after a couple frustrating days.