The EvalFunc only works with plaintext modulus up to p = 8 (see the paragraph here about GenerateLUTviaFunction). I don’t see what inputs you use. Also, returning from FHEW to CKKS works when the message is significantly smaller than the plaintext modulus (see the above link, as well as the example, which for p = 8 reduces the range of the message by quite a lot.
To implement ReLU, a much better option is to use scheme switching to compute the sign of you ciphertext, for instance, with EvalCompareSchemeSwitching, which returns a vector of elements encrypting zero for positive values and 1 for negative values, and then multiply your ciphertext by (1-sign). See also How to calculate ReLU function through ciphertext conversion? - #2 by andreea.alexandru.