Confusing as hell.
It is “Neither of the solutions [were] affected” if it’s talking about the past, and it is “Neither of the solutions [are] affected” if talking about the present.
The only wrong option is, ironically, “is”, as “is” is reserved for singulars, not plurals.
Saying “Neither of the solutions [is] affected” sounds terrible and isn’t proper English grammar.
- Native speaker