Cannot confirm trade(gift) on steam authenticator

Solution 1:

Relog into your account. In the menu on the bottom-left you have the option to logout. Than login again. If this does not solve the issue, try reinstalling the application on your mobile phone.

First, remove the application from your phone (android / apple)
Second, find the app in the play-/app-store and install it.
-This step will require you to authenticate the account.
-Choose the option 'I don't have access to mobile authenticator'
-Choose to receive your code via text message
-Enter the received code and verify the account

Now you should be logged in again and should be able to confirm any trade-deals.