Unsure what this error message means

Exception ‘MethodError: no method matching +(::Base.RefValue{Any}, ::NamedTuple{(:contents,), Tuple{Matrix{Float64}}})
Closest candidates are:
+(::Any, ::Any, !Matched::Any, !Matched::Any…) at operators.jl:560
+(!Matched::Union{MathOptInterface.ScalarAffineFunction{T}, MathOptInterface.ScalarQuadraticFunction{T}}, ::T) where T at /home/ubuntu/.julia/packages/MathOptInterface/MMUy6/src/Utilities/functions.jl:1783
+(!Matched::Union{InitialValues.NonspecificInitialValue, InitialValues.SpecificInitialValue{typeof(+)}}, ::Any) at /home/ubuntu/.julia/packages/InitialValues/OWP8V/src/InitialValues.jl:154
…’ occurred while calling julia code:

hmm, what code generated this error?

Is this optimization function from a package, or has it been defined somewhere else in your code? And what’s the value of x0 here?

Showing us more of your code, and also pasting a more complete stacktrace of the error, will help a lot with figuring it out.