[15:32:25 ERROR]: [ImageOnMap] Exception : java.lang.NoSuchMethodException: net.minecraft.server.v1_16_R3.PacketPlayOutChat.<init>(net.minecraft.server.v1_16_R3.IChatBaseComponent, net.minecraft.server.v1_16_R3.ChatMessageType) at java.lang.Class.getConstructor0(Class.java:3349) ~[?:?] at java.lang.Class.getConstructor(Class.java:2151) ~[?:?] at fr.zcraft.imageonmap.quartzlib.tools.text.MessageSender.sendChatPacket(MessageSender.java:524) ~[?:?] at fr.zcraft.imageonmap.quartzlib.tools.text.MessageSender.sendMessage(MessageSender.java:169) ~[?:?] at fr.zcraft.imageonmap.quartzlib.tools.text.MessageSender.sendSystemMessage(MessageSender.java:390) ~[?:?] at fr.zcraft.imageonmap.quartzlib.tools.UpdateChecker.lambda$getDefaultPlayerNotificationSender$3(UpdateChecker.java:229) ~[?:?] at fr.zcraft.imageonmap.quartzlib.tools.UpdateChecker.lambda$onPlayerJoin$4(UpdateChecker.java:248) ~[?:?] at org.bukkit.craftbukkit.v1_16_R3.scheduler.CraftTask.run(CraftTask.java:100) ~[patched_1.16.5.jar:git-Paper-585] at org.bukkit.craftbukkit.v1_16_R3.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:468) ~[patched_1.16.5.jar:git-Paper-585] at net.minecraft.server.v1_16_R3.MinecraftServer.b(MinecraftServer.java:1413) ~[patched_1.16.5.jar:git-Paper-585] at net.minecraft.server.v1_16_R3.DedicatedServer.b(DedicatedServer.java:418) ~[patched_1.16.5.jar:git-Paper-585] at net.minecraft.server.v1_16_R3.MinecraftServer.a(MinecraftServer.java:1328) ~[patched_1.16.5.jar:git-Paper-585] at net.minecraft.server.v1_16_R3.MinecraftServer.w(MinecraftServer.java:1116) ~[patched_1.16.5.jar:git-Paper-585] at net.minecraft.server.v1_16_R3.MinecraftServer.lambda$a$0(MinecraftServer.java:289) ~[patched_1.16.5.jar:git-Paper-585] at java.lang.Thread.run(Thread.java:834) [?:?]

Already aware of this issue, thanks for posting logs :). The PR #163 will fix this