Error when adding to FluentBoards: Underfind method

I found a little more info. When I try to add a subtask and the error appears, I checked the Network calls in my browsers developer tools. It shows this: subtasks?query_timestamp=1789706... Fromt the URL https://mydomain.tld/wp-json/fluent-boards/v2/projects/1/tasks/40/subtasks?query_timestamp=1748970654876 Method: GETrequest | Status Code: 400 Bad Request | Referrer Policy: same-origin

access-control-allow-headers
Authorization, X-WP-Nonce, Content-Disposition, Content-MD5, Content-Type
access-control-expose-headers
X-WP-Total, X-WP-TotalPages, Link
allow
GET, POST
cache-control
no-cache, must-revalidate, max-age=0, no-store, private
cf-cache-status
DYNAMIC
cf-ray
94a0ce840dd11f26-DEN
content-length
75
content-type
application/json; charset=UTF-8
date
Tue, 03 Jun 2025 17:10:56 GMT
expect-ct
max-age=86400, enforce
expires
Wed, 11 Jan 1984 05:00:00 GMT
link
<https://mydomain.tld/wp-json/>; rel="https://api.w.org/"
nel
{"success_fraction":0,"report_to":"cf-nel","max_age":604800}
referrer-policy
same-origin
report-to
{"endpoints":[{"url":"https:\/\/a.nel.cloudflare.com\/report\/v4?s=111..."}],"group":"cf-nel","max_age":604800}
server
cloudflare
server-timing
cfL4;desc="?proto=TCP&rtt=38482&min_rtt=19862&rtt_var=8623&sent=1199&recv=672&lost=0&retrans=1&sent_bytes=572927&recv_bytes=325511&delivery_rate=2590050&cwnd=283&unsent_bytes=0&cid=1c7a6cbc5241f580&ts=586868&x=0"
strict-transport-security
max-age=15552000; includeSubDomains; preload
x-content-type-options
nosniff
x-frame-options
SAMEORIGIN
x-powered-by
PHP/8.2.27
x-qm-overview-memory
211.9 MB
x-qm-overview-memory_usage
20.7% of 1,024 MB server limit
x-qm-overview-time_taken
1.1671
x-qm-overview-time_usage
0.1% of 1,500s limit
x-robots-tag
noindex
x-wp-nonce
f95eaf6e07
x-xss-protection
1; mode=block
:authority
mydomain.tld
:method
GET
:path
/wp-json/fluent-boards/v2/projects/1/tasks/40/subtasks?query_timestamp=1748970654876
:scheme
https
accept
*/*
accept-encoding
gzip, deflate, br, zstd
accept-language
en-US,en;q=0.9
cookie
mycookie; wp-settings-time-1=1748969246
dnt
1
priority
u=1, i
referer
https://mydomain.tld/wp-admin/admin.php?page=fluent-boards
sec-ch-ua
"Brave";v="137", "Chromium";v="137", "Not/A)Brand";v="24"
sec-ch-ua-mobile
?0
sec-ch-ua-platform
"Windows"
sec-fetch-dest
empty
sec-fetch-mode
cors
sec-fetch-site
same-origin
sec-gpc
1
user-agent
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/137.0.0.0 Safari/537.36
x-requested-with
XMLHttpRequest
x-wp-nonce
f95...

Resolved.