ERROR: R _ProjectSprite: invalid sprite frame 0/0

[Roser]

Hello to the person who is reading this, I am going to put in context, I try to make a SOC with a custom sprite, the free slot:

freeslot ("MT_HEARTBOMB", "SPR_HRBM")

the sprite is named HRBMA0

the soc is this

S_THROWNEXPLOSION1 status
SpriteName = HRBM
SpriteFrame = A
Duration = 1
Next = S_THROWNEXPLOSION2
Action = A_ThrownRing
Var1 = 0
Var2 = 0

MT_HEARTBOMB object
MapThingNum = 100
SpawnState = S_THROWNEXPLOSION1
SpawnHealth = 1000
SeeState = S_NULL
SeeSound = sfx_cannon
ReactionTime = 8
AttackSound = sfx_None
PainState = S_NULL
PainChance = 192 * FRACUNITY
PainSound = sfx_None
MeleeState = S_NULL
MissileState = S_NULL
DeathState = S_RINGEXPLODE
XDeathState = S_NULL
DeathSound = sfx_pop
Speed = 60 * FRACUNITY
Radius = 16 * FRACUNITY
High = 24 * FRACUNITY
DispOffset = 0
Mass = 100
Damage = 1
ActiveSound = sfx_None
Flags = MF_NOBLOCKMAP | MF_MISSILE
RaiseState = S_NULL

and the complete error is: R_projectsprite: invalid sprite frame 0/0 for HRBM