I logged in using Chrome (the only browser Otzar likes) and got the same thing:

תחת תחזוקה ישוב לפעילות בקרוב

Could they be maintaining the site?  That happens every so often.

We got no advance warning of this situation, but we seldom do.

Try again later.  We only a finite number of simultaneous users allowed to access this database at any one time.  Occasionally, you will be unlucky  unlucky, and be the user who has exceeded our limit.