Any of containers log not shipping to destination

I have tried the configuration shared in this repo,

As per the link given for fargate(https://github.com/aws-samples/amazon-ecs-firelens-examples/tree/mainline/examples/fluent-bit/config-file-type-file) I have write extra.conf and build fluentbit custom image by copying extra.conf in Dockerfile

I have attach extra.conf and Dockerfile below, you can review this.

But there is some problem in it or missing something, because When I tried this, any of my application container logs not shipping to datadog even stdout logs are also not shipping.
Can anybody do a review & suggest best possible solution or correct me if there is something wrong or missing anything in my approach.

NOTE: In my case destination is datadog & ${APP_LOG_FILE_PATH} will be set as environmental variable of container.

**extra.conf**

[SERVICE]
Flush 5
Grace 30
Daemon off

[INPUT]
Name tail
Tag app-logs
Buffer_Chunk_Size 1mb
Buffer_Max_Size 100mb
Mem_Buf_Limit 250mb
Path ${APP_LOG_FILE_PATH}
Refresh_Interval 5
Path_Key source
Skip_Empty_Lines true

[OUTPUT]
Name datadog
Match *
Host http-intake.logs.datadoghq.com
TLS on
compress gzip
apikey #apikey
dd_service datadog-logging
dd_source fluentbit-test
dd_message_key log

**Dockerfile**

FROM public.ecr.aws/aws-observability/aws-for-fluent-bit:stable
COPY ./extra.conf /fluent-bit/etc/extra.conf

Start by comparing the supplied extra.conf and Dockerfile with the linked FireLens config-file example. Check how the custom image loads the configuration and how the tail input and Datadog output are configured, then reproduce the setup with the reported environment variable. Done means identifying the missing or incorrect configuration and confirming that application and stdout logs reach Datadog.

Written by the indexing model from the issue text.