owner is unable to invite guests

We've come across a strange scenario when a client is trying to access resources on our tenant.  The client users are able to redeem their invitations.  However, on subsequent attempts to access resources on our tenant, they keep on receiving an error on the O365 sign in page stating "account or password is incorrect".  However, if they sign into portal.office365.com first and then past the link to our resources, they can get in.  Has anyone else come across this or know what the cause may be?  Are there any AAD settings on our clients tenant that may be preventing users directly signing into another tenant?  Appreciate any advise or knowing if others are experiencing the same.