Hi. There is not quite enough information to go on in your question. There could be quite a few things misconfigured which could make it unable to link.
We have quite a few Force 300 PTP links... some only a couple km, but some links up to 25 km - all working as expected, and working really well especially considering the cost of the gear. The longer links are F300c with 2' or 3' antennas on them, but still working very well for us.
However, there are lots of incorrect possible settings to which could result in then not being able to link... and unfortunately, the eAlign won't be any help until you are at least linked.
What verson of the Firmware are you using? (I'd recommend the 4.5 release version)
What mode are you using - TDD or ePTP? (If you're using 4.5, I'd recommend ePTP mode)
What power output settings are you using? In ePTP mode, you need to manually specify power output.
Are you using DFS Channels?
On the SM/SLAVE, do you have all the channels 'checkmark' so that it's scanning as expected?
Can you post screen shots of your AP/SM Config -> Radio screens from both sides? That will at least give us a starting point.