Memory limit in RStudio on a Windows Server 2012 VM

I am using RStudio on a windows server 2012 Virtual Machine.
I get the memory allocation error "Error: cannot allocate vector of size 6.9 GB" when I try to merge 2 tables.

I have tried all the steps I found on other stack answers, with no luck.

1. I used the gc() function
2. I increased the memory limit with memory.limit(size=500000)
3. I checked the version of R in use is 64 bit
4. I checked the OS is 64 bit
5. I have played around with different VM settings, going up to 128GB RAM.

Is there a hard limit in Widows Server that cannot change?

Thanks a lot.