Our website used to rank in a good position on Google search in our country, for the last 3 years, when anyone searched for the main product we sell. About 1 month ago the Homepage Title changed on Google search results when we search for the website, altough we changed nothing. We've always kept the Homepage Title as "Product X - Homepage Title", and 1 month ago Google search replaced this for "Homepage Title: Product X", and we are not listed anymore on the first page of Google search results.
For this project we don't need a SEO optimization of our website. For this project we just need to find the source of the problem outside our website. Why did the Homepage Title change on Google search and why did we lost our relevance? Was there any blacklist problem or maybe did someone with bad intention build a link chain against us? For this project we need to find the source of the problem outside our website.