We have a SalesForce Field that has been established for a couple of year now is missing the information in Marketo. The field has information in SalesForce for all of the leads/contacts, however some of the Marketo profiles do not have that field filled out. I know the field is synching correctly because profiles that are being created today have the field filled out in both systems.
What can I do so the profiles that don't have the field filled can be update?
Are you saying that data does not exist for that field in some leads/contacts in Marketo?
If the fields are sync'd properly, you can trigger update from SFDC. Simplest way is to update any unimportant (sync'd) field in SFDC for those people. This will trigger lead/contact update from SFDC to Marketo.
Yes some of the leads/contact do not have the data in Marketo, but have information for that same field in SalesForce.
Remember that Marketo only syncs records that have changed since the last sync. If some people have values updated in that field but not others, that sounds like those contacts/leads haven't been updated (their systemmodstamp) modified in SFDC a while, so their data hasn't completely synced with Marketo. If you are concerned this is an issue, force a record update across all those records which have failed to sync in Salesforce which will force their resync to Marketo.
To rule out permissions problems, I recommend you log into Salesforce using the Marketo sync user's login and try to update that field manually on one or two of those records.