I created a campaign. Why don't I see any campaign in the look up field when I try to convert a lead?
In the Convert Lead page, the Campaign Source field lists only those campaigns with which the selected lead (that is being converted) is associated. It does not list all campaign records available in your Campaigns module. So please check if the lead has been associated to any campaign.
A lead could also be associated to more than one campaign. When you convert the lead, the Campaign Source field lets you select the campaign which qualified the lead to a deal. Once converted, the Contact record will have all the campaigns that were associated to the lead, while the Deal record will have only the campaign source that you selected during lead conversion.