[15:56:02] [Server thread/ERROR]: Could not load 'plugins\lifesteal-smp-plugin-1.5.1.2.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: Unsupported API version 1.17
at org.bukkit.craftbukkit.v1_16_R3.util.CraftMagicNumbers.checkSupported(CraftMagicNumbers.java:361) ~[patched_1.16.5.jar:git-Purpur-1171]
at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:149) ~[patched_1.16.5.jar:git-Purpur-1171]
at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:414) ~[patched_1.16.5.jar:git-Purpur-1171]
at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:322) ~[patched_1.16.5.jar:git-Purpur-1171]
at org.bukkit.craftbukkit.v1_16_R3.CraftServer.loadPlugins(CraftServer.java:393) ~[patched_1.16.5.jar:git-Purpur-1171]
at net.minecraft.server.v1_16_R3.DedicatedServer.init(DedicatedServer.java:279) ~[patched_1.16.5.jar:git-Purpur-1171]
at net.minecraft.server.v1_16_R3.MinecraftServer.w(MinecraftServer.java:1074) ~[patched_1.16.5.jar:git-Purpur-1171]
at net.minecraft.server.v1_16_R3.MinecraftServer.lambda$a$0(MinecraftServer.java:293) ~[patched_1.16.5.jar:git-Purpur-1171]
at java.lang.Thread.run(Thread.java:831) [?:?]

"org.bukkit.plugin.InvalidPluginException: Unsupported API version 1.17"

The plugin does not work on 1.16.5, Please upgrade to 1.17 while I work on trying to get it on 1.16.5-1.17.x+