can't create file.ffindex from file.ffdata

[minhphi1712]

I tried to create file index of a3m.ffdata but i can't
Error:
ffindex_build -f -s a3m_final.ffindex uniclust30_2018_08_a3m_100M.ffdata
a3m_final.ffindex: File exists

I tried deleting the old file to force the new command, but it still shows that error.
After I executed the command a ffindex file is created but it has nothing in it

My a3m.ffdata format
#tr|C4PYW0|C4PYW0_SCHMA Ubiquitin-specific peptidase 48 (C19 family) OS=Schistosoma mansoni OX=6183 GN=Smp_125860 PE=4 SV=2

tr|C4PYW0|C4PYW0_SCHMA_consensus
ME
tr|C4PYW0|C4PYW0_SCHMA Ubiquitin-specific peptidase 48 (C19 family) OS=Schistosoma mansoni OX=6183 GN=Smp_125860 PE=4 SV=2
ME
#sp|P83570|GWA_SEPOF Neuropeptide GWa OS=Sepia officinalis OX=6610 PE=1 SV=1
sp|P83570|GWA_SEPOF_consensus
GW
sp|P83570|GWA_SEPOF Neuropeptide GWa OS=Sepia officinalis OX=6610 PE=1 SV=1
GW