Summing even fibonacci numbers in lisp

Question

I've just started learning Lisp, and I'm working through some Project Euler problems. I'm stuck on the one where you sum the even Fibonacci numbers below a max number. The things I've tried follow. I've read this post but I'm still not sure why neither of my ways works!

CL-USER> (defun sum-even-fibs (max)
           (do ((curr 0 next)
                (next 1 (+ curr next))
                (sum  0 (if (evenp curr) (+ sum curr))))
               ((> max curr) sum)))
SUM-EVEN-FIBS
CL-USER> (sum-even-fibs 10)
0


CL-USER> (defun sum-even-fibs (max)
           (let ((sum 0))
             (do ((curr 0 next)
                  (next 1 (+ curr next)))
                 ((> max curr))
               (if (evenp curr) 
                   (setq sum (+ sum curr))))
             (format t "~d" sum)))
SUM-EVEN-FIBS
CL-USER> (sum-even-fibs 10)
0
NIL

Answer 1

Slightly 'better' version of the answer of arbautjc:

(loop for a = 0 then b and b = 1 then (+ a b) 
      while (< a 4000000) 
      when (evenp a) sum a)