'Verification Failed' Error When Attempting To Log Into Apple Services

This issue comes after the one raised in my previous post. When my iPad entered it's dearie sleep after it being powered off and not turning back on before an attempted series of restarts and forced restarts on 25 August, this also had an eerie effect on the accessibility of Apple services. iCloud being one that I noticed the night of my iPad going dark. I had attempted to make sure I could still access my files saved to the Cloud, however the site blasted my correct credentials. The same message popping up every time I attempt to log in, regardless of device. 'Verification Failed'. 'An unknown error occurred'. Any guidance on this issue by anybody with the expertise willing to give their input would be appreciated.