Problem:
During promotion of specific version of API from one environment to another, webMethods API Gateway generates following error:
The API with name <SomeAPIName> and system version <SomeVersionNumber> cannot be added to the version chain, because there are missing version numbers. Try to use the option Fixing missing versions.
Sample error message would be something like “The API with name MyAPIName and system version 5 cannot be added to the version chain, because there are missing version numbers. Try to use the option Fixing missing versions.“
Scenario Details:
Suppose you have multiple versions of an API (i.e. version 1 to version 5) in source environment and you have only version 1 of same API in destination environment and now you want to promote a specific version (lets say version 5) of that particular API to destination environment using promotion option in webMethods API gateway. Upon trying to promote version 5 (to destination environment), you may see above mentioned error in API gateway promotion report telling you that version 5 cannot be added to the version chain of API in question.
Solution:
In this case, during promotion, select the check box “Fix missing version” as shown below:
When this “Fix missing versions” check box is selected, then any discrepancy in API versions in source & target environment is fixed/solved during Promotion.
For example suppose you have three version of API ‘MyAPI’ in source environment and the destination environment has only version 1 of ‘MyAPI’ and now you want to promote only version 3 of the same API to destination environment then if you select check box “Fix missing version” during promotion then existing version 1 of ‘MyAPI’ in ‘destination’ will be linked to newly promoted version ‘3’ of same API in destination. However, if you don’t select check box “Fix missing version” during promotion, then in this particular scenario you may get error during promotion similar to the one mentioned above in this post.
Mubarik Ahmed - Integration Blog 