It is possible that SCIA Engineer can't be installed when the Avira antivirus is used.
SCIA Engineer uses a ZenSupp.dll file for the installation of the software. ZenSupp contains some crypting tools.
The problem is that the same tools are sometimes used by viruses. For that reason, Avira will mark the ZenSupp.dll file as a virus and the installation of SCIA Engineer can't be completed.
It is recommended to use another antivirus instead of Avira.
The ZenSupp.dll used by SCIA Engineer is completely safe. This can be checked by scanning the file on this page: https://www.virustotal.com/