Is this WPA2 Password uncrackable?

here is the command line:
hashcat64.exe -m 2500 -a3 davehash.hccapx -1 0123456789abcdefghijklmnopqrstuvqxyzABCDEFGHIJKLMNOPQRSTUVWXYZ ?1?1?1?1?1?1?1?1?1?1?1?1

I receive this error:

The wordlist or mask that you are using is too small.
This means that hashcat cannot use the full parallel power of your device(s).
Unless you supply more work, your cracking speed will drop.
For tips on supplying more work, see: https://hashcat.net/faq/morework
Approaching final keyspace - workload adjusted.

#
I know that password is from a-z,0-9 ,A-Z and 12 characters long.
Is this just too many charterers? 

I am new to hashcat, so please be gentle with terminology and abbreviations please.

Thank you