All conditions listed in the Dependencies section of a rule need to be met in order for the rule to be executed. In your screenshot, the field name 'Actual Final Analysis Plan (SAP):' is listed twice, once for null and once for before the value of another field. If the field is null, it probably meets both conditions. If there is a value in the field, though, it is no longer null and the rule will not be executed.
It would not be necessary to restart the server to have rule changes take effect. You should refresh the browser window, though. My only other suggestion is to try a test with only the one rule enabled just to eliminate the possibility that another rule is undoing this one.
Keep in mind that the caches are maintained by the application to improve performance. Every time a cache is cleared the entries have to be pulled from the database instead of the cache. In order to minimize the impact on performance you should only clear the caches related to entities that you change manually with direct database queries. An example would be when we change user information in user registration entries, we clear only the Users cache. Any change that you make through a PPM interface should not require clearing any cache as the cache entries should be updated automatically in all nodes. If it is not, it is a defect.