Anti-cheat and antivirus have something in common: both are protective software that watches your system closely and distrusts anything unusual. Most of the time they coexist fine. Occasionally, they get suspicious of each other.
Why a conflict can happen
The friction comes from similarity. Antivirus looks for software behaving in ways malware does — running deep, inspecting other processes, loading drivers. An anti-cheat does exactly those things, for legitimate reasons. To an antivirus that has never seen a particular anti-cheat, that behaviour can look alarming. From the other side, an anti-cheat is wary of any software inspecting or modifying the game's process — and some antivirus features do touch running programs. Each is doing its job; the job descriptions just overlap.
What a conflict looks like
The symptoms are recognisable. An antivirus may flag or quarantine an anti-cheat component, after which the game refuses to start because its protection is missing. A game may report an anti-cheat error or a generic "untrusted system" message. Performance stutters can appear when two pieces of deep software get in each other's way. None of this means either program is broken — it means they have not been told to trust each other.
How to resolve it
The usual fixes are straightforward. Keep both the antivirus and the anti-cheat (and the game) updated, since vendors add recognition of each other over time. If an antivirus has quarantined a known anti-cheat component, restoring it and adding an exclusion for that game's anti-cheat resolves it. Reinstalling the anti-cheat through the game's repair option can also help. The goal is simply to tell the two programs the other is expected.
A note of caution
Add exclusions thoughtfully. An exclusion is you vouching for that software, so only exclude an anti-cheat you installed by installing a legitimate game from an official source. "Disable your antivirus to run this" coming from an unofficial download is a warning sign, not an instruction.
The takeaway
Anti-cheat and antivirus conflict occasionally because both watch the system deeply and can mistake each other for a threat. The fixes are ordinary — update both, restore and exclude a wrongly-quarantined component — and the only caution is to vouch for software only when you know it is genuine.