There are a couple of reasons as to why you may be unable to export MP3 files from FL Studio, these include unsupported sample rates and LAME encoder issues. If you receive the above error message when exporting MP3 files you can refer to the following solutions.
Unsupported Sample Rate
The MP3 standard ONLY supports 44.1 or 48 kHz sample rates. Your FL Studio sample rate must be set to one of the supported sample rates in order to successfully export MP3 files.
1. Navigate to 'Options > Audio Settings'.
2. Confirm that the selected Sample Rate is set to either 44100Hz or 48000Hz.
Can't export MP3 files from FL Studio 11 after installing FL Studio 12
The following solution should correct the issue:
You should now be able to export your projects to MP3 in FL Studio 11.
Image-Line Support Team