Saving the tq5 and tq6 file is not a good way to backup your LOTW certificates, you need to export the certificate as pk12 file.
Open tQSL cert application, click as your desired callsign’s cert to backup
Right click on it and click save and save it on your computer. Now you can upload pk12 file to your servers, or attach it on email.
For more info, please read http://www.arrl.org/files/file/LoTW%20Instructions/LoTW%20in%20a%20second%20or%20new%20computer_2012_07_31.pdf