While attending Search Marketing Summit Sydney I was asked of the attendees to take a look at their HREFLang implementation. They had spent hours looking at it but Google still gave errors saying they did not have alternatives set. As we have identified before, one of the reasons the search engine cannot find your alternatives if you have set a global canonical on the local pages.
I this example, if we review the source on the Singapore page, https://www.examplesite.com/sg/ we see the HREFLang Element is correct but look before and you will see that the Singapore page has a canonical set to the global site. As such, search engines will not index the /sg pages resulting in a hreflang alternate “not found error”.
It is critical to test to ensure that the canonical on each page is correct and IS not another language page or a global page.
Note: We have added canonical checking to the HREFLang Testing Tool.