SORRY FOR BAD ENGLISH
when i put skin name in head with skull-owner, the head stay normal being alex or steve and in the console appears [ItemJoin] The player could not be found!

Could you provide the item in question so I can check your settings.
Pastebin.com link of your items.yml would be ideal.

I have the same problem.

Server version: PaperSpigot-"4c7641d" (MC: 1.8.8)
ItemJoin version: ItemJoin v5.2.2-RELEASE-b734 by RockinChaos
SkinsRestorer version: v14.1.3

Item config:
profile:
id: SKULL_ITEM:3
skull-owner: '%player%'
slot: 1
name: '&b%player%'
lore:
- '&7Great for setting a players profile,'
- '&7as seen in mini-game servers.'
itemflags: inventory-modify, death-drops, unbreakable, hide-durability, hide-attributes, self-drops, overwrite, item-store
triggers: join, respawn, world-change
enabled-worlds: ALL

Console error:

[01:29:33 WARN]: java.lang.NoSuchMethodException: net.skinsrestorer.bukkit.SkinsRestorer.getInstance() [01:29:33 WARN]: at java.lang.Class.getMethod(Unknown Source) [01:29:33 WARN]: at me.RockinChaos.itemjoin.utils.api.DependAPI.getSkinValue(DependAPI.java:205) [01:29:33 WARN]: at me.RockinChaos.itemjoin.handlers.ItemHandler.setStoredSkull(ItemHandler.java:417) [01:29:33 WARN]: at me.RockinChaos.itemjoin.handlers.ItemHandler.setSkullOwner(ItemHandler.java:402) [01:29:33 WARN]: at me.RockinChaos.itemjoin.item.ItemMap.setSkull(ItemMap.java:3980) [01:29:33 WARN]: at me.RockinChaos.itemjoin.item.ItemMap.updateItem(ItemMap.java:3599) [01:29:33 WARN]: at me.RockinChaos.itemjoin.item.ItemMap.getItem(ItemMap.java:3575) [01:29:33 WARN]: at me.RockinChaos.itemjoin.item.ItemUtilities.lambda$setInvSlots$5(ItemUtilities.java:568) [01:29:33 WARN]: at org.bukkit.craftbukkit.v1_8_R3.scheduler.CraftTask.run(CraftTask.java:59) [01:29:33 WARN]: at org.bukkit.craftbukkit.v1_8_R3.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:352) [01:29:33 WARN]: at net.minecraft.server.v1_8_R3.MinecraftServer.B(MinecraftServer.java:783) [01:29:33 WARN]: at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:378) [01:29:33 WARN]: at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:713) [01:29:33 WARN]: at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:616) [01:29:33 WARN]: at java.lang.Thread.run(Unknown Source)

Confirmed as a bug, the issue is now resolved in the latest snapshot.
Link; https://ci.craftationgaming.com/job/ItemJoin/764/
Remember to remove your old ItemJoin.jar file
Let me know!~

Officially fixed in the latest release,

You can now download it here; https://www.spigotmc.org/resources/itemjoin.12661/download?version=431799