My password worked at 1password.com, but not in app on iPad or Mac

So far, things are OK on my MacBook, but I'm still having problems on my iPad. I've attached a screenshot to illustrate the problem. As you'll see, I was trying to login at a site called Shopper+. On the website's login page, the 1Password icon appears in the Username field, but rather than filling in the username and password, it pops up with "Use 1Password". When I click on the icon, I then get a popup asking me to enter my password for 1Password. When I enter it, you can see that it is not accepted. If I try tapping on the "eye" icon to show what I have entered, the icon just disappears and the password is not revealed. But I've done this so many times I'm quite sure I've entered the correct password.

If I pull up the 1Password app, I am able to login to it OK. It's just when I'm using Safari to login to a website that this problem occurs.

When I use my MacBook to login to this same website, and I click on the 1Password icon in the website's Username field, I get a popup asking me to use either Touch ID or my 1Password account password. If I select the latter option, I get the same popup as on the iPad, but when I enter my password, it's accepted. I have no idea what's causing the problem on the iPad. Incidentally, I have enabled Touch ID on the iPad as well, but in this situation I'm not offered the option of using it.

Here's the screenshot: