RE: Portal redeem invitation removing 'I have an existing account' check box
Hi Steve,
Unchecking "I have an existing account" will not have any effect.
invitation codes are almost exclusively used to allow existing contacts to be joined with login credentials, which means the user should leave the I have an existing account checkbox unchecked.
However, there are other uses for invitation codes – they can be used to give users additional web roles, or you can use them to run classic workflows when the invitation code is redeemed. In those cases, invitation codes might be redeemed by users that can already login to the portal.
In short, the I have an existing account checkbox controls whether the user is redirected to the Sign In page or the Registration page after clicking the Register button. If they already have an account, they go to the Sign In page; if they don’t, they go to the Register page.
Also, you can hide it:
Create a new Content Snippet - Account/RedeemInvitation/PageCopy and paste below code in portal Management app:
You can refer following link for more details:
Engineered Code - Blog - Power Apps Portals: Hide the Existing Account Checkbox on the Redeem Invitation Page