Run the Gaussian calculation with the output structure as the new geometry.

I agree with Sweta Kumari. The simplest solution is to start from the latest optimization step and increase the number of cycles. The gif file could be as follows:

%nproc=

%mem=

%oldchk=

%chk=

#p method chkbasis geom=allcheck guess=read integral=ultrafine scf=(novaracc,xqc,maxcycle=1024) opt pop=full gfinput gfprint

By using the allcheck option you do not need to type comment, charge, spin multiplicity or anything else but am empty line.

I hope this helps!