You need a higher level of permission. Sorry, you are not allowed to customize

Hi,

Seen a few topics on this, but with no clear resolution:

When I try to customize, I receive:
You need a higher level of permission.
Sorry, you are not allowed to customize this site.

Gave me that message when I first tried, but was then able to customize a few days ago.
Today it's reverted back to giving me the same denied access. So it's not a consistent error.

Is it a GP, Bluehost or WP issue?
How do I customize my site without constantly being denied access?

Thanks.