error: root must be bracketed in zriddr

[Amoghsriv]

I've modified the class to incorporate a different scalar field model, namely the Ratra-Peebles Model. I'm facing some issues while running the file. Here is the error I'm facing.
While running CLASS, I'm getting the error

Not using attractor initial conditions
Not using attractor initial conditions
Not using attractor initial conditions
Not using attractor initial conditions
Not using attractor initial conditions
Not using attractor initial conditions
Not using attractor initial conditions
Not using attractor initial conditions
Not using attractor initial conditions
Not using attractor initial conditions
Not using attractor initial conditions
Not using attractor initial conditions
Not using attractor initial conditions
Not using attractor initial conditions
Not using attractor initial conditions
Not using attractor initial conditions
Running CLASS version v3.3.0
Computing background

Error running background_init
=>background_init(L:819) :condition (pba->shooting_failed == TRUE) is true; Shooting failed, try optimising input_get_guess(). Error message:

input_shooting(L:653) :error in input_find_root(&xzero, &fevals, ppr->tol_shooting_deltax_rel, &fzw, errmsg);
=>input_find_root(L:963) :error in input_fzero_ridder(input_fzerofun_1d, x1, x2, tol_x_rel*(((fabs(x1))<(fabs(x2))) ? (fabs(x2)) : (fabs(x1)) ), pfzw, &f1, &f2, xzero, fevals, errmsg);
=>input_fzero_ridder(L:1118) :error; root must be bracketed in zriddr.

The ini file I'm using is

#Input Parameters

h = 0.67810
omega_cdm = 0.1201075
omega_b = 0.02238280
Omega_scf = 1.0

8.b) If Omega scalar field is different from 0

8.b.1) Scalar field (scf) potential parameters and initial conditions

(scf_parameters = [scf_lambda, scf_alpha, scf_A, scf_B, phi,

phi_prime]). V = ((\phi-B)^\alpha + A)exp(-lambda*phi), see

http://arxiv.org/abs/astro-ph/9908085. If 'attractor_ic_scf' is set to

'no', the last two entries are assumed to be the initial values of phi

in units of the reduced planck mass m_Pl and the conformal time

derivative of phi in units of [m_Pl/Mpc]. (Note however that CLASS

determines the initial scale factor dynamically and the results might

not be as expected in some models.)

scf_parameters = 0.5, 0.4, 0.0, 0.0, 5.0, 0.0

8.b.2) Scalar field (scf) initial conditions from attractor solution (assuming

pure exponential potential). (default: yes)

attractor_ic_scf = no

8.b.3) Scalar field (scf) shooting parameter: If Omega_scf is set (can only be negative),

the following index (0,1,2,...) in the list scf_parameters will be used for shooting:

(See also the section about shooting in input.c)

Basically parameter number scf_tuning_index will be adjusted until

the correct Omega_scf is found to suffice the budget equation

#Output Parameters
headers = yes
write_parameters = yes
write_warnings = yes
background_verbose = 3
write_background = yes

Thankyou for your help!