Some users have reported that a second instance of X-Plane starts after signing in to the Simlink app. All reports have in common that Firefox is the default system browser.
This is caused by an incorrect application mapping in Firefox settings. To fix, follow this procedure:
Open Firefox Options. Under General, scroll down to Applications.
Find the row “navigraph-traffic-desktop”. This is likely mapped to Use X-Plane, which is not correct.
Press the dropdown arrow on the right hand side (see image below) and choose Navigraph Simlink.
- Close options. Now after the Simlink signing process, it should not open a second instance of X-Plane but function normally.