Gradle 6/Java 11 "module not found" error for poi and poi-ooxml but jars exist

I'm having an issue that has been driving me crazy for days. I'm relatively new to the Java modular system but was managing to declare my dependencies correctly until I started to use poi.

Here is my build.gradle snippet (gradle v 6.4):

dependencies {

implementation 'org.springframework.boot:spring-boot-starter-web'
implementation 'org.slf4j:log4j-over-slf4j:1.7.30'

implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
implementation 'commons-net:commons-net:3.6'
implementation 'com.google.guava:guava:28.1-jre'

implementation 'org.apache.poi:poi:4.1.2'
implementation 'org.apache.poi:poi-ooxml:4.1.2'

}

Here are the poi jars correctly located in my gradle cache:

~/.gradle/caches/modules-2/files-2.1/org.apache.poi$ tree
.
├── poi
│   └── 4.1.2
│       ├── 964bf41cf68bce08e4ef6b2279b559fdf8d454f4
│       │   └── poi-4.1.2.jar
│       ├── 9ce4c76815903772b25324d8419df2d3fe227f4d
│       │   └── poi-4.1.2.pom
│       └── ac5af3832ebaef94562a39591a000338bbae0e4b
│           └── poi-4.1.2-sources.jar
├── poi-ooxml
│   └── 4.1.2
│       ├── 712cc02d5bbe729d2485a1579f3d8dfc47e25b51
│       │   └── poi-ooxml-4.1.2-sources.jar
│       ├── 87d9a22aa9a7dd26e80c360e709f7ee02e32ab3b
│       │   └── poi-ooxml-4.1.2.jar
│       └── ccbcde71e4f0fdfa80e1007dd1babfc9828c629e
│           └── poi-ooxml-4.1.2.pom

Here is my module-info.java:

module template {
    requires spring.core;
    requires poi;
    requires poi.ooxml;
}

Here is the error I get on running gradle clean build:

error: module not found: poi
    requires poi;
             ^

Things I have tried:

1. Deleting my gradle cache and doing a complete --refresh-dependencies build
2. Finding all the poi and poi-ooxml subdependencies and adding to the build.gradle
3. Using "api" instead of "implementation" for poi and poi-ooxml in the build.gradle

I am at my wits end on this -working on my day off! - and could really appreciate some input.