ringer circuit old telephone
If this is your 1000 pF timing cap you will be court-martialled.





Otherwise:

Temporarily short U1 drain to source - it MAY be current limiting for reasons best known to itself. (And/or measure voltage drop across it during operation. Should be close to zero). 

Set supply you are using to current limit and short out R3 (0.25 Ohms (0.27 on your board)). This is a current limiting resistor which can cause problems if set wrong. Looks OK though.

Place a small capacitor (0.001 probably OK, maybe 0.01 uF) across R14/47k. This improves transient response and noise response and can help heaps on occasion. 

R6 = 180R should be fine if that as they have specified. I do not know what the load is but R6 provides drive current to the internal Darlington second stage. At Vring ~= 3.8V then drive ~~ 3V/180R =~~ 16 mA. I don't know Beta of the 2nd transistor in the Darlington but say = 25 gives Vout max = 400 mA which should be OK. (About 1 Watt ringing).

Check all pins during operation to be sure they are at voltages you'd expect.
 1 = 0/Vring/55V approx.
 2 = hard ground.  

Advise results.

Tell Sparkfun that the world rotates the other way (outputs are meant to be at right of circuit) and that pin numbers on circuit diagrams are obligatory.