Magento2 : Cron run not working

Question

Below given is crontab.xml

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Cron:etc/crontab.xsd">
<group id="customemarsys_cron">
    <!-- catalog Related Jobs -->
    <job name="custom_product_sync" instance="Custom\Module\Cron\ProductSync" method="execute">
        <schedule>* */1 * * *</schedule>
    </job>
</group>

cron_groups.xml

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Cron:etc/cron_groups.xsd">
<group id="customemarsys_cron">
    <schedule_generate_every>15</schedule_generate_every>
    <schedule_ahead_for>20</schedule_ahead_for>
    <schedule_lifetime>15</schedule_lifetime>
    <history_cleanup_every>10</history_cleanup_every>
    <history_success_lifetime>10080</history_success_lifetime>
    <history_failure_lifetime>10080</history_failure_lifetime>
    <use_separate_process>0</use_separate_process>
</group></config>

I tried to run php -dmemory_limit=6G bin/magento cron:run --group customemarsys_cron

But it reflects error

main.WARNING: Could not acquire lock for cron group: customemarsys_cron, skipping run [] []

Answer 1

As far as I know there are 2 cron groups by default in Magento 2: default and index.
Try to change your cron group to default and check again:

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Cron:etc/crontab.xsd">
<group id="default">
    <!-- catalog Related Jobs -->
    <job name="custom_product_sync" instance="Custom\Module\Cron\ProductSync" method="execute">
        <schedule>* */1 * * *</schedule>
    </job>
</group>

Answer 2

Try to execute following sql query in phpmyadmin and then execute your cron.

SELECT RELEASE_ALL_LOCKS();

Answer 3

bin/magento cron:install [--force]

Use --force to rewrite an existing Magento crontab. https://devdocs.magento.com/guides/v2.4/config-guide/cli/config-cli-subcommands-cron.html