In some cases, you may see a word with spaces shown as a misspelling, even though the word looks correct on the live page. This can happen because Siteimprove checks your page's HTML code rather than the content presented in the browser.
To investigate this further, you can look at the misspelling Page Report and click on "Show HTML" on the top of the page. Then you will see the misspelling highlighted within the HTML code. The reason for the space is usually obvious in the HTML view. Often it is because of an HTML tag (e.g. <span>) in the middle of a word.
Your options are to fix the error in the HTML code using your CMS or approve the misspelling on that particular page.