ISSNs are not included in an APA 7th reference list or in a Chicago 17th bibliography.
APA 7th
Where no DOI is given for an electronic resource, do not include a URL including database information in the reference. Where an electronic article has been found on the internet (i.e. not through a library search), give the full URL to the web page where it was found.
Chicago 18th Notes & Bibliography
In the absence of a DOI, look for a persistent link, often available with the electronic resource, e.g.:
http://www.jstor.org/stable/23356366.
A persistent link, also known as a stable link, or permalink, is a URL that connects directly to a specific article in a library database or online journal. The URL in the browser window is often not a persistent/stable URL.
Sometimes a suitable URL will not be available and in such cases, include the name of the database rather than the URL
