EV indicator not appearing

Hi,
I have problem in high voltage battery and I did replace around ten cells.
Next day the mechanic remove the catalytic converter (manifold and converter)
and put another one that is empty from reduction oxidation pads for transient use.
And told me to return after two days until new catalytic converter is available to install it.
Once return home I noticed that EV mode did not appear again in my dashboard. My question is, what do you think is the cause?
Is it battery problem or catalytic converter?
Note: after change cells the EV indicator was present when battery charged, but after changing catalytic converter thus problem appeared. No trouble codes appear and faulty signs appearing on dashboard.
Please help.
Thank you.