Why am I getting inf or nan likelihood?

I mostly just in general has difficulties to understand why some of my models don’t work, for example this one also throughs an error:

import pymc3 as pm
import numpy as np


syn = np.array([0, 113, 42, 78, 125, 234, 393, 874, 407, 439, 297, 322, 246, 434, 797, 365, 202, 554, 303, 564, 392, 243, 237, 123, 206, 254, 243, 309, 388, 551, 810, 554, 741, 716, 483, 428, 267, 198, 190, 196, 387, 248, 249, 348, 857, 260, 296, 451, 339, 461, 426, 481, 1038])


with pm.Model() as model:
    alpha = pm.Exponential('alpha', lam=5)
    beta = pm.Exponential('beta', lam=5)

    g = pm.Gamma('g', alpha=alpha, beta=beta, observed=syn)

    trace = pm.sample(return_inferencedata=True, cores=1)

it gives me this error: