Can my employer affect whether my claim gets approved?

Your employer is not responsible for approving your claim; your employer's insurance company is.

If you have sustained a workplace injury, you should definitely inform your employer about it as soon as possible. It'll also be good to inform them of your decision to lodge a workers comp claim.

However, once you've lodged your claim with SIRA, the decision for approval lies with your employer's insurance company.

Hence, your employer has no influence over the outcome of your workers comp claim.