Hi sandy2beachin,
I would start with the same questions that I asked the original poster...
When you took your CATs:
1) Did you take the ENTIRE CAT (including the Essay and IR sections)?
2) Did you take them at home?
3) Did you take them at the same time of day as your Official GMAT?
4) Did you ever do ANYTHING during your CATs that you couldn't do on Test Day (pause the CAT, skip sections, take longer breaks, etc.)?
5) Did you ever take any of these CATs before?
Your self-assessment while you were taking the GMAT was clearly 'off', so there are likely other factors to consider besides the ones above. The GMAT gave you the score that you EARNED though - the 'log-in issue' had NO impact on how you were scored.
Thankfully, the GMAT is a predictable, standardized Test, so you CAN train to score at a higher level. We just need to properly define what was inaccurate about your practice and what you could have better done to maximize your performance on Test Day.
GMAT assassins aren't born, they're made,
Rich