LTSpice error when simulating behavioural voltages
V1 is a symbol instance. You need to use the voltage of a node in your behavioural expression.
It's not clear without digging around at the schematic what LTSpice will have called the node on the top of your V1 symbol. It's best to label it manually. Use the \$\boxed{\text{A}}\$ tool on the toolbar to add a label to the relevant node.
Your equation should be V=0.0487*V(NodeLabel)+0.838