I've tried the removing the config_4 file after exiting Viewer to install my free license, the 31 day trial is back - but I can't add the license file when I drag it. I tried opening the license file in Notepad and copying the text as well and that didn't work for me either. Any suggestions?
Could you please clarify what version of Remote Utilities do you use? In case if you use version 18.104.22.168, please note that your license key from version 6 is not compatible with it. In this case, please generate a new key using this form. You will receive your key as file with a .rlicense extension - with this key you can register your Viewer as described here.