Search volume missing for some hot keywords

[wang liao]

Hi,

I found some hot keywords, which is generic and have many people search everyday obviously, but when I try fetch the historic data  through Google Ads API v21: generateKeywordHistoricalMetrics, there is no data, for example, the keywords 'fibromyalgia'  is a generic word and obviously have many people search on Google, while I got this from generateKeywordHistoricalMetrics API:

{
  "results": [
    {
      "text": "fibromyalgia"
    }
  ]
}

I've checked through Google Trends and some third-part tool like SEMrush, I've believe the keywords should have abundant data.