Can’t login to Morrison’s Mymorri Account

I have updated My iPhone 12 to IOS 15 and I can no longer log in to my Morrison’s work account which is :

I use this account for work to view my payslips and complete my online training courses at work.

I also tried to use the solutions from this website(https://www.myfeedbackcard.com/mymorri/) but it doesn't seem to work.

can anybody suggest anything to resolve this situation, please?

many thanks, Nancy