Error while installing pythia-pgs

I ran 'install pythia-pgs' and ran into this error.
I have ubuntu 21.04 installed. Is this because of my OS version?

----- Now compiling PGSLIB -----

gfortran -fno-automatic -c -o ./lib/pgslib.o ./src/pgslib.f
./src/pgslib.f:1027:72:

 1027 | 3 T = 0.5*T
      | 1
Warning: Fortran 2018 deleted feature: DO termination statement which is not END DO or CONTINUE with label 3 at (1)
./src/pgslib.f:1028:72:

 1028 | 2 U(II) = S
      | 1
Warning: Fortran 2018 deleted feature: DO termination statement which is not END DO or CONTINUE with label 2 at (1)
./src/pgslib.f:1031:72:

 1031 | 4 TWOM24 = 0.5*TWOM24
      | 1
Warning: Fortran 2018 deleted feature: DO termination statement which is not END DO or CONTINUE with label 4 at (1)
./src/pgslib.f:2727:17:

 2727 | pt1 = v4pt(p1)
      | 1
Error: Rank mismatch in argument ‘p’ at (1) (rank-1 and scalar)
./src/pgslib.f:2728:17:

 2728 | pt2 = v4pt(p2)
      | 1
Error: Rank mismatch in argument ‘p’ at (1) (rank-1 and scalar)
./src/pgslib.f:2780:38:

 2780 | pgs_kt_beam_distance = v4pt(p1)**2
      | 1
Error: Rank mismatch in argument ‘p’ at (1) (rank-1 and scalar)
./src/pgslib.f:2784:42:

 2784 | pgs_kt_beam_distance = 1.0/v4pt(p1)**2
      | 1
Error: Rank mismatch in argument ‘p’ at (1) (rank-1 and scalar)
./src/pgslib.f:5267:22:

 5267 | del_phi = v4phi(p) - v4phi(q)
      | 1
Error: Actual argument contains too few elements for dummy argument ‘p’ (3/4) at (1)
./src/pgslib.f:5267:33:

 5267 | del_phi = v4phi(p) - v4phi(q)
      | 1
Error: Actual argument contains too few elements for dummy argument ‘p’ (3/4) at (1)
make[2]: *** [Makefile:126: lib/libpgslib.a] Error 1
make[2]: Leaving directory '/home/friskyspock/MG5_aMC_v3_1_0/pythia-pgs/libraries/PGS4'
make[1]: *** [makefile:72: libpgs] Error 2
make[1]: Leaving directory '/home/friskyspock/MG5_aMC_v3_1_0/pythia-pgs/src'
make: *** [makefile:3: all] Error 2

Please help me with this error