When signing in to online Shaw Webmail, message says 'Security Check Failed. Clear your browser cache and retry'. Screenshot attached. Have done so in "Clear browsing and data history", (as per Firefox guidelines) multiple times, for all History and cache. Did not resolve issue. Contacted Shaw Support; they instructed to try logging in with Chrome browser. Worked fine. Issue appears to be strictly with Firefox Browser (on multiple devices). I prefer Firefox over Chrome. Any advice greatly appreciated.