Cause
You assigned the same device tag to two or more main functions in the schematic.
Solution
Possibility 1
Assign different device tags to the main functions.
Possibility 2
If you meant to assign the device tag several times, make one of the functions the main function and all the other functions auxiliary functions in the property dialog. To this purpose the property dialog of the respective function contains the Main function check box in the Symbol / function data tab that you have to activate or deactivate correspondingly.
Then start a new check run.
Tip:
Use automatic numbering when inserting symbols. Select the menu item Options > Settings > Projects > "Project name" > Devices > Numbering (online). Under On symbol insertion, select the option Number.