@llawsa you might want to take a look at this:
OTA and Blynk.begin() - #19 by PeteKnight
Basically, some things have changed in the latest Arduino core, and you need to be connected to WiFi before calling ArduinoOTA.begin. If you have your Blynk.begin towards the end of your void setup, but Initialise your OTA before that then it won’t work.
Pete.