If you have problems getting your blockchain to sync (especially a repeating error in yellow about “unknown top block”), make sure your computer’s clock is correct. Fixing the clock fixed the problem.
I’ve heard of this issue with other coins too. Makes sense.
Here’s how to make your Windows machine update current time automatically:
In Linux, the fix is different depending on your distro, so google
Auto time update on Linux + (your distro’s name)
This is what the “unknown top block” error looks like: