If you are running Dolphin in "Portable Mode" (with a portable.txt file in the folder), the emulator may struggle if placed in a protected directory like C:\Program Files . How to Fix the "Failed to Write New FST" Error 1. Configure Windows Defender / Antivirus
The most common solution is to allow Dolphin through your security software. dolphin ios-fs failed to write new fst
Many security suites, including Windows Defender, use a feature called "Controlled Folder Access" that blocks unknown applications from writing to the "Documents" folder where Dolphin defaults its data. If you are running Dolphin in "Portable Mode"
The Dolphin folder may be set to "Read-Only," or the user may lack administrative rights to modify files in that directory. including Windows Defender
Either turn it off entirely or click and add Dolphin.exe .