Igor,
Two things:
a) "Sign up now" is not equivalent to "Login": signing up means "registering", not logging in for something that one already is registered for
b) the human eye is trained to see specific things: in the current situation, one focuses on
- the central text and search box
- when not logged in yet (!), one can be distracted by cookie notifications (hiding the "sign up button" in some cases)
- the "blue sign up button" (when not blocked by notifications) is relatively "invisible" due to size and color scheme
and it is probably better to place the login form in a centered fashion OR in the row with "Forum Members Badges" (just place the login button on the right of this row).
In summary, it is a matter of text ("Login" instead of "Sign up") and a matter of place of the login form (keep the central focus and replace the login form to be more visible).
Note that there is actually value in using both a separate "Login button" and a "Sign up button": it can provide incentives to register, if one is new on the forum.
Hence, as an alternative, one can place two buttons below the search form, to make optimal use of the value of two buttons.
Naturally, these are mere suggestions.
Regards......