About 7% of our audience logs in to Qlik Cloud using a mobile device (as opposed to a Desktop). Is your device access controlled by a central IT function? The behavior sounds similar to what happens when www.qlikcloud is not an accepted domain (not white listed by an IT control).
If this is not the cause, reach out and let me know and we can schedule a moment to see what is going on and preventing your access.
Director, Product Mgmt, Qlik Cloud