you can simply copy-paste your maple input to make it easier for others to view what you've done. Warning: I don't know a single thing about what you're doing. I couldn't find any info about with*(physics), so I replaced it with : with(Physics). I copy the output below. I hope it may provide a hint.

> restart: with(Physics);

[*, ., Annihilation, AntiCommutator, Bra, Bracket, Check,

Commutator, Coordinates, Creation, Dagger, Define, Dgamma,

FeynmanDiagrams, Fundiff, Intc, Inverse, Ket, KroneckerDelta,

LeviCivita, Parameters, Projector, Psigma, Setup, Simplify,

SpaceTimeVector, Trace, Vectors, ^, dAlembertian, d_, diff,

g_]

> Define(A[mu, nu, lambda, rho], antisymmetric = {{mu, nu, lambda}}):

> Define(B[sigma, alpha, rho, beta], antisymmetric = {{rho, alpha, sigma}}):

> Define(C[sigma, alpha, mu, rho], antisymmetric = {{mu, alpha, sigma}}):

> Define(D[rho, nu, lambda, beta], antisymmetric = {{nu, rho, lambda}}):

> Define(E[sigma, alpha, nu, rho], antisymmetric = {{rho, alpha, sigma}}):

> Define(G[mu, rho, lambda, beta], antisymmetric = {{mu, rho, lambda}}):

> Define(H[sigma, alpha, lambda, rho], antisymmetric = {{alpha, lambda, sigma}}):

> Define(F[mu, nu, rho, beta], antisymmetric = {{mu, nu, rho}}):

> fundamentalidentity := AB = CD+EG+HF:

> constraintp := Define(P[p, q, r, 0], antisymmetric = {{p, q, r}}) = LeviCivita[p, q, r]:

> constraintq := Define(Q[p, q, r, s], antisymmetric*{{p, q, r}}) = 0:

> mu := 0:

> v := p:

> lambda := q:

> printlevel := 1:

Defined objects with tensor properties

Defined objects with tensor properties

Defined objects with tensor properties

Defined objects with tensor properties

Defined objects with tensor properties

Defined objects with tensor properties

Defined objects with tensor properties

Defined objects with tensor properties

Error, (in Define) expected spacetime, spinor or gauge indices but the indices in P[p,q,r,0] are of not of those types

Error, (in Define) expected objects with a tensor structure, from a symbol, say A, to an indexed function, say A[mu](X). Received: {antisymmetric*{{p, q, r}}}

> for rho from 0 to 3 do for p to 3 do for q to 3 while p < q do for sigma from 0 to 3 do for alpha from 0 to 3 while alpha < sigma or alpha < rho do for beta from 0 to 3 do for r to 3 while r < q or r < p do for s to 3 do solve({fundamentalidentity, A = constraintp, A = constraintq, B = constraintp, B = constraintq, C = constraintp, C = constraintq, D = constraintp, D = constraintq, E = constraintq, F = constraintp, F = constraintq, G = constraintp, G = constraintq, H = constraintp, H = constraintq}, [A]) end do end do end do end do end do end do end do end do;

>