Cannot customize message “An error occurred while submitting your form.”

Please look at the last line of the markup generated by Sureform. There you will find the markup with the uneditable error message:

 <p id="srfm-error-message" class="srfm-error-message" hidden="true">There was an error trying to submit your form.
        Please try again.</p>

See full markup:

<form-data" id="srfm-form-1509" class="srfm-form " form-id="1509" after-submission="hide form" message-type="same page"
    success-url="" ajaxurl="http://blank.local/wp-admin/admin-ajax.php" nonce="4bc2ccce8f">
    <input type="hidden" id="sureforms_form_submit" name="sureforms_form_submit" value="4d05c8983f"><input type="hidden"
        name="_wp_http_referer" value="/">
    <input type="hidden" value="1509" name="form-id">
    <input type="hidden" value="" name="srfm-sender-email-field" id="srfm-sender-email">
    <input type="hidden" value="" id="srfm-page-break">
    <input type="hidden" value="" name="srfm-honeypot-field">
    <div data-block-id="74d02424"
        class="srfm-block-single srfm-block srfm-input-block srf-input-74d02424-block srfm-block-width-33-33 1509">
        <div class="srfm-block-wrap">
            <input class="srfm-input-common srfm-input-input" type="text"
                name="srfm-input-74d02424-lbl-VGV4dCBGaWVsZA-srfm-input" id="srfm-input-74d02424-lbl-VGV4dCBGaWVsZA"
                aria-describedby="srfm-error-74d02424" data-required="true" data-unique="false" maxlength="100" value=""
                placeholder="Text Field *" data-srfm-mask="none">
        </div>
        <div class="srfm-error-wrap">
            <div class="srfm-error-message" data-srfm-id="srfm-error-74d02424" data-error-msg="This field is required."
                data-unique-msg="Value needs to be unique.">This field is required.</div>
        </div>
    </div>

    <div data-block-id="af2fabad"
        class="srfm-block-single srfm-block srfm-gdpr-block srf-gdpr-af2fabad-block srfm-block-width-100 1509">
        <div class="srfm-block-wrap">
            <input class="srfm-input-common screen-reader-text srfm-input-gdpr" id="srfm-gdpr-560350691"
                name="srfm-gdpr-af2fabad-lbl-SSBjb25zZW50IHRvIGhhdmUgdGhpcyB3ZWJzaXRlIHN0b3JlIG15IHN1Ym1pdHRlZCBpbmZvcm1hdGlvbiBzbyB0aGV5IGNhbiByZXNwb25kIHRvIG15IGlucXVpcnku-srfm-gdpr"
                aria-describedby="srfm-error-af2fabad" data-required="true" type="checkbox">
            <label class="srfm-cbx" for="srfm-gdpr-560350691">
                <span class="srfm-span-wrap">
                    <svg class="srfm-check-icon" width="12px" height="10px" aria-hidden="true">
                        <use xlink:href="#srfm-gdpr-af2fabad-check"></use>
                    </svg>
                </span>
                <span class="srfm-span-wrap srfm-block-label">I consent to have this website store my submitted
                    information
                    so they can respond to my inquiry. <span class="srfm-required" aria-label="Required"><span
                            aria-hidden="true"> *</span></span></span>
            </label>
            <svg class="srfm-inline-svg" aria-hidden="true">
                <symbol id="srfm-gdpr-af2fabad-check" viewBox="0 0 12 10">
                    <polyline points="1.5 6 4.5 9 10.5 1"></polyline>
                </symbol>
            </svg>
        </div>
        <div class="srfm-error-wrap">
            <div class="srfm-error-message" data-srfm-id="srfm-error-af2fabad" data-error-msg="This field is required.">
                This
                field is required.</div>
        </div>
    </div>


    <div class="srfm-submit-container ">
        <div style="width: ; text-align: left" class="wp-block-button">
            <button style="width:" id="srfm-submit-btn" class="srfm-btn-frontend srfm-button srfm-submit-button">
                <div class="srfm-submit-wrap">
                    Submit <div class="srfm-loader"></div>
                </div>
            </button>
        </div>
    </div>
    <p id="srfm-error-message" class="srfm-error-message" hidden="true">There was an error trying to submit your form.
        Please try again.</p>
    </form>