Indexing Issues. Multistores and Google Search Console

[Sergei.dev]

We used to have two separate stores — nailpro.fi and nailszone.eu.
At some point, we decided to merge them into a multistore setup.

Now we have a multistore consisting of:
Website – Languages available on it:
• nailpro.fi – FI / EN / RU
• nailszone.eu – EN / FI / RU / DE / FR / IT / ES / ET
• nailszone.es – ES / EN / RU
• nailszone.it – IT / RU / EN
• nailszone.fr – FR / RU / EN
• nailszone.de – DE / RU / EN

All websites have been added to Google Search Console, but some of them are not being indexed.
Indexed: nailpro.fi, nailszone.eu, nailszone.fr
Not indexed: nailszone.es, nailszone.it, nailszone.de

By “not indexed,” I mean that Google shows “Discovered – currently not indexed” and the total number of indexed pages is 0, and this situation has remained the same for several months.

 

I tried to investigate the issue and modified head.tpl to adjust the link rel="alternate" settings, but nothing changed. (You can check the code on any of the sites.)

I also noticed that the robots.txt file contained only one sitemap link — for the main site — so I added sitemap links for all other stores as well.

What can I do to ensure that all websites get indexed and start working properly for their target countries?