Couple of questions....

Can we have two of us logged in to the same account at the same time?

And should we be able to log in on an android tablet?

I'm currently logged in on my laptop; my husband is unable to log in on his tablet.

I am logged in on my windows machine & the App & the portal on my phone.

So dont see why not

I’ve sometimes found I get a blank page - then noticed the website was open on my phone, so perhaps there is an issue or limit?

You shouldn't have any issues with multiple logins. We don't have a limit for logins per account.