Still cannot combine split with curly brackets

Question

I tried to use vphantom{...} and overleaf does not take breaqn package, so I still have the question:

I have the following formula, but I get an error with it that I can't fix. What is wrong here really?

 \begin{equation}
 \begin{split}
     \psi(x)=\sum_{j=1}^l\sum_{v=0}^{m_j-1}U_v(x,\mu)V_{m_j-1-v}(\psi,\mu)\left|_{\mu=\mu_j}\\
     +\int_{-\infty}^{\infty}\frac{\sqrt{\mu}}{\pi\alpha(\sqrt{\mu})\alpha(-\sqrt{\mu})}\left\{e^+(x,\sqrt{\mu})e^+(\psi,-\sqrt{\mu})\\+e^-(x,\sqrt{\mu})e^-(\psi,\sqrt{-\mu})\right\}d\mu
  \end{split}
 \end{equation}

The preamble is:

\documentclass{article}
\usepackage{hyperref}
\usepackage{amssymb}
\usepackage{MnSymbol}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\newcommand{\norm}[1]{\left\lVert#1\right\rVert}
\newcommand{\R}{\mathbb{R}}
\newcommand{\C}{\mathbb{C}}
\newcommand\Setst[3][big]{\csname #1l\endcsname\{ #2 : 
  \begin{array}[t]{@{}l@{}}#3\csname #1r\endcsname \}\end{array}}
\usepackage{amssymb}
\usepackage{amsfonts}
\usepackage{mathtools}
\usepackage[mathscr]{euscript}
\usepackage{mathrsfs}
\usepackage{yfonts}
\usepackage{setspace}
    \doublespacing
\usepackage{imakeidx}
\makeindex[columns=1, title=Alphabetical Index]


\newcommand{\footremember}[2]{%
    \footnote{#2}
    \newcounter{#1}
    \setcounter{#1}{\value{footnote}}%
}
\newcommand{\footrecall}[1]{%
    \footnotemark[\value{#1}]%

and the comment by overleaf is:

Extra }, or forgotten \right.
Missing \right. inserted.
Missing } inserted.
Extra \right.
Missing { inserted.

Thanks