The error log is indicating an OutOfMemoryException when Schoolcomms is trying to import data from SIMS, specifically when importing Behaviours/Achievements/Groups.
Although the PC may have available RAM, Schoolcomms requires a certain amount of 'contiguous' memory during the import process (i.e. a block of memory that is together) depending on the size of the data provided to us by SIMS, in order for the import to complete successfully. The error you are experiencing essentially means that the data object being passed to Schoolcomms from SIMS was too large to be processed, due to the sheer volume of data being imported.
It is best to try running the import on another PC. Alternatively, it may be worth closing all other programs before running the Schoolcomms import, as this may free up the required amount of contiguous memory available.