What you describe in your post suggests a faulty thermostat.
If the temperature light never goes off, the thermostat isn't switching.
Check that the probe in the oven hasn't been dislodged or damaged when you changed the element.
If it's ok, I'm afraid you'll need to obtain and fit a new thermostat.
Check it out, see what you find and get back to me if you need more help.
If you have the electronic version, I'm afraid it's most likely the main control board that has failed.
Hope this helps
I can'y rate just yet as I have yet to source and fit a thermostat to hopefully fix the problem.
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