First, Make sure you are using .config and not .cfg for configuration files, and the syntax was also changed from :
# org.apache.jackrabbit.oak.plugins.document.DocumentNodeStoreService.cfg
#MongoDB server details
mongodburi=mongodb://aem:aempassword@mongodbserver1.customer.com:27000],mongodbserver2.customer.com:27000#Name of MongoDB database to use
db=aem
#Store binaries in custom BlobStore e.g. FileDataStore
customBlobStore=true
cache=2048
blobCacheSize=1024
To
#org.apache.jackrabbit.oak.plugins.document.DocumentNodeStoreService.config
#Mongo server details mongouri="mongodb://aem:aempassword@mongodbserver1.customer.com:27000],mongodbserver2.customer.com:27000" #Name of Mongo database to use
db="aem"
#Store binaries in custom BlobStore
customBlobStore=B"true"
cache=I"2048"
blobCacheSize=I"1024"