chrome won't open pdf or txt files anymore

For the PDFs check Settings > Privacy and security > Site settings > Additional content settings > PDF documents. If it's set to download PDFs, that's your downloads. Switch it to open in Chrome. The blank tab on both PDF and txt smells like an extension though. Try the same file in an incognito window (extensions are off there by default). If it opens fine, go through chrome://extensions and turn them off one at a time. PDF editors and download managers are the usual suspects, they grab file links. A reset doesn't always clear it if it's a work laptop, chrome://policy will show if something is being forced.