3.55 CFWs are outdated and not supported anymore. There's little to no reason to stay on 3.55 these days.
Just extract you eEid Root Key if you ever plan on using DEX and install Rebug 4.41.2 on top of your 3.55 CFW from XMB by following the guide below:
1- Make NOR/NAND dump (optional):
Install latest version of multiMAN (4.40.00), plug in a FAT32 formatted USB flash drive into the right USB port, launch multiMAN under Games and go to mmOS > Press [O] on any file > Open in HEX viewer > Press [SELECT] > Press [START] > Export GameOS LV2: Select No > Export HV LV1: Select No > Export FLASH: Select Yes
2- Install Rebug 4.41.2 from XMB:
Download Rebug 4.41.2 from Rebug's website, verify the md5 hash, rename the PUP to PS3UPDAT.PUP, put it on your FAT32 formatted flash drive in PS3\UPDATE, go to System Update and Update via Storage Media. Make sure there's NO original game disk in the drive and that you DON'T Update via Internet or else you would risk installing OFW higher than 3.55!
3- Enable QA:
Install Rebug Toolbox from Package Manager, launch it under Games, go to Utilities and enable QA. This is to ensure easier and safer downgrading.