There’s one time I encountered this error when executing a bash code/script:
install.sh: Syntax error: "(" unexpected
The script does not begin with a shebang line, so the kernel executes it with /bin/sh. On Ubuntu, /bin/sh is dash, a shell designed for fast startup and execution with only standard features. When dash reaches the line, it sees a syntax error: that parenthesis doesn’t mean anything to it in context.
Since dash (like all other shells) is an interpreter, it won’t complain until the execution reaches the problematic line. So even if the script successfully started at some point in your testing, it would have aborted once the problematic line was reached.
The shebang line must be the very first thing in the file. Since you use bash features, the first line of the file must be #!/bin/bash or #!/usr/bin/env bash.