Hi
I don't know what your workflow design.
Suggest that you can create workflow task with item ID in some field.
I always add the item ID in workflow task Description filed.
So you can get the item easily very much after that.
And spservice is not useful very much, maybe you can try to sp plus.
https://aymkdn.github.io/SharepointPlus/
Please remember to mark the replies as answers if they helped.
Linyu - SharePoint Engineer
QQ Group: 72637444