I find that occasionally, some anti-virus and firewall software can false-flag updated Stellaris exe as "unrecognized" or a "threat". Try checking it out. Maybe it's been isolated. :)

######################### VERSION 2.3.3 ##########################
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# Ancient Relics Story Pack Features
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* A number of archaeology sites have been overhauled to give more interesting rewards for completion, with new techs, empire modifiers, and ethics-based outcomes###################
# General
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* Updated localisation for all languages###################
# Balance
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* Further changed Precursor system spawning to always connect to an owned system, if possible, to reduce them appearing... Read more