updated version of OS for mac book air inaccessible.
Hello, I have not used my computer mac book air for years; the current version of the software is 10.13.6 (10.13.6 (17G14042) FOR A 13-inch, Early 2015.
Unfortunately, I do not seem to find a version of an updated software;
None are offered when clicking on updating software.
any ideas on how I should proceed?