TST, hard to say anything definitive without a lot more data, but if SQL doesn't need more than 32GB it won't necessarily allocate more.
Check that nothing else on the server is consuming a lot of memory. Make sure you don't have large pages enabled. If it's a VM, check what the reserved memory is for that guest.
Are there signs of memory pressure? Is SQL under any load?
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability