CDO

I am trying to merge multiple nc files using cdo mergetime

#!/bin/bash

# Get list of files in directory
files=$(ls /xxxxx/Input/trial/tas_Amon_UKESM1-0-LL_1pctCO2*.nc)

# Loop over realizations
for r in $(echo "$files" | sed -E 's/.*_r([0-9]+)i.*/\1/' | sort -u); do
    # Get list of files for current realization
    r_files=$(echo "$files" | grep "_r${r}i")

    # Get smallest and largest timestamps
    times=$(cdo showtimestamp $r_files | cut -d ' ' -f 1 | sort | uniq)
    smallest=$(echo $times | cut -d ' ' -f 1)
    largest=$(echo $times | cut -d ' ' -f $(echo $times | wc -w))

    # Merge files for current realization
    cdo mergetime $r_files /xxxxx/Input/trial/tas_Amon_UKESM1-0-LL_1pctCO2_r${r}i1p1f2_gn_${smallest}-${largest}.nc
done

But I still get the error "cdo command not found" when I run the script.
Any idea what could be wrong?