The looper can be a bit tricky to get going at first but once you get it set up things run pretty smoothly.  Remember the looper must be v30 or higher.  It will say v30 on the SD card.  

1.  When you try and enter looper mode by holding down the right and middle stompswitches what happens? 

     a. the first preset LED lights up blue - if so you are in looper mode

     b. nothing happens - looper mode has not been enabled or your firmware has not been updated, see the FAQ for updating the Reverb or Echosystem.  Read below to enable looper mode. 

     c. the preset lights flash red - the SD card cannot be read.  Will talk more about that below.  

Enable Looper

- enter Advanced Configuration: hold LEFT and RIGHT stompswitches, hit SHIFT/SAVE 

- rotate MODE till PLATE /TAPE is lit GREEN

- turn decay/delay time all the way up, preset LED should go to #2 

- the looper is now enabled 

If you don't see a Green Plate/Tape option, then your pedal is not up to date and you need to instal the latest firmware to use the looper.

If the Preset Lights Flash Red

The SD card is not recognized or compatible with the looper.  Did you insert the SD card after booting up the pedal? power cycle the pedal and see if it works, the SD card is not hot-swappable and will flash red if you insert it after powering on the pedal. 

A lot of off brand cards seem to give the looper problems, so I recommend buying a card from a brand you recognize.  
The looper requires an SD card that is V30 or higher and SDHC.  SDXC cards should work as well, it will say SDHC on the face of the card.  

The card does not have to be FAT32 and will corrupt any data on the card. Try clearing the card and  reformatting the card to FAT32 or exFat if you get red flashing lights.  If you format to exFat the looper will still work but it won't work for updating the pedal.  

A couple other things could go wrong here.

1.  The card is locked: There will be a switch on the left side of the SD card to lock it.  

2.  The Switch is broken: If the lock switch on the side of the card breaks the looper can fail while still working occasionally. I actually recommend the card pictured, it is a pretty good card despite the broken switch.  

3.  The SD card is broken or failed.  Even if it worked previously SD cards can break or fail in various ways and I would recommend testing with another SD card.  Connect it to your computer to see if you can reformat it and try again.