While Modbus TCP is inherently an open protocol, the client software itself needs updates to remain compatible with modern Windows security protocols.
This issue is likely due to permissions and is not common. Try creating the folder C:\simplymodbus\licenses\ before entering the key. This may help the program "remember" the license key. simply modbus tcp client license key upd
Create the folder C:\simplymodbus\licenses\ before entering the key. Also ensure you have proper write permissions to the program folders. While Modbus TCP is inherently an open protocol,
In some rare cases, major OS overhauls or changes to partition structures can alter the registry pathways or system signatures that the software checks. Step-by-Step: How to Update Your License Key This may help the program "remember" the license key
| Error Message | Likely Cause | Fix | |---------------|---------------|------| | Key not valid for this version | You have a license for v8 but installed v9 | Download the older version or pay for a version update. | | Activation limit reached | Key used on too many machines | Deactivate old installations or request a reset from support. | | Unable to contact license server | Firewall or proxy blocking outbound traffic | Allow simplymodbus.ca port 80/443 or use offline activation. | | Key has expired | Temporary or trial key used beyond allowed period | Purchase a full license. | | Corrupt license store | Windows registry or file corruption | Uninstall, delete leftover folders in %AppData% , reinstall, and re-enter key. |