This key only valid for older version of Camtasia Studio version 8.1.2

You can download it here
https://www.techsmith.com/download/oldversions

Select the version: v8.1.2 [2013 Jul 2015]

SCA93-TCCNC-CDUCC-ADVS5-D54AA
SCA93-TCCNC-CDUCC-ADVS5-D54AA
CFCC9-RCCNA-C9F5H-HM9CC-L98CE
XBMA2-N4ACC-CJMCC-5LN7A-M486R
SCFCC-Q4CEZ-CNC5M-C4P4B-K5AM6
MACCF-8CDJA-C6HSD-MBHXC-PB3DC
CD4YB-QKBHC-FWRCC-CHC4R-LCB65
MA9PC-9CXBG-ASVZC-CCCAD-52ED8