If you have trouble installing an IntelliTAG, first ensure that it is has not already been paired with the Somfy One / One +. To do this, go to the "System" menu, and verify that it is not listed.
Next, verify that the IntelliTAG is within radio range of the Somfy One / One +. To do this, try to install the IntelliTAG having first brought it close to the Somfy One / One +. Go to the "System" menu, tap the "+" sign in the upper right corner, and follow the prompts.
If the battery tab has already been removed, remove the battery and then put it back in when you are prompted to remove the tab.
Finally, make sure there is not a problem with the battery by restarting the operation using a brand new battery.