Pebble can't install app in any way - cloudpebble or command line

I've enjoyed developing simple apps for my pebble watch, but since yesterday I cannot install any new ones on my phone (I do have spare slots on pebble).

I've tried installing old (working) apps via cloudpebble portal, but I get following:

Saving
Compiling
Preparing to install app
Installation rejected. Check your phone for details.
(Phone message: There was an error trying to install the provided app.)

So I've tried installation through a command line:

$ pebble install --cloudpebble -vvvv

But this is the output:

INFO:requests.packages.urllib3.connectionpool:Starting new HTTP connection (1): 209.118.208.39
DEBUG:pebble_tool.util.analytics:Queueing analytics data: {'platform': 'native_sdk', 'data': {}, 'event': 'invoke_command_install', 'identity': {'sdk_client_id': '93381446-f47e-4be5-bd4a-781af1f42c3a', 'user': u'55b8844a6638300025560100'}, 'sdk': {'project': {'sdk': u'3', 'is_watchface': True, 'type': 'native', 'uuid': '2737c550-fd8a-4e70-82be-1b887e5d7a4d', 'app_name': u'MoveInGrid'}, 'host': {'platform': 'Darwin-15.2.0-x86_64-i386-64bit', 'python_version': '2.7.10', 'is_vm': False}, 'version': u'3.8.2', 'tool_version': '4.0.1'}}
DEBUG:requests.packages.urllib3.connectionpool:"HEAD / HTTP/1.1" 301 0 INFO:requests.packages.urllib3.connectionpool:Starting new HTTPS connection (1): td.getpebble.com
DEBUG:requests.packages.urllib3.connectionpool:"POST /td.pebble.sdk_events HTTP/1.1" 200 0
Waiting for phone to connect...
Connected.
DEBUG:libpebble2.communication:-> WatchVersion(command=None, data=WatchVersionRequest())
DEBUG:libpebble2.communication:-> 0001001000
DEBUG:libpebble2.communication:<- 00960010015509b4fb76322e392e31000000000000000000000000000000000000000000000000000035343636346264000005015222545f76312e352e350000000000000000000000000000000000000000000000000000316331363237350001050152e2f83256335233000000000051313536303535453030513604750648b4b026658a035509b4fb656e5f55530000015858585858585800
DEBUG:libpebble2.communication:<- WatchVersion(command=1, data=WatchVersionResponse(running=WatchFirmwareVersion(timestamp=1426699515, version_tag=v2.9.1, git_hash=54664bd, is_recovery=False, hardware_platform=5, metadata_version=1), recovery=WatchFirmwareVersion(timestamp=1377981535, version_tag=v1.5.5, git_hash=1c16275, is_recovery=True, hardware_platform=5, metadata_version=1), bootloader_timestamp=1390606386, board=V3R3, serial=Q156055E00Q6, bt_address=04750648b4b0, resource_crc=644188675, resource_timestamp=1426699515, language=en_US, language_version=1, capabilities=24866934413088856, is_unfaithful=None))
Installing app...
App install failed.
INFO:root:Spent 0.001597 seconds waiting for analytics.

I've tried several things to resolve this issue:

creating new project from provided template;
disconnecting the watch;
watch factory reset;
iOS pebble app reinstallation;
creating and linking to a new cloudpebble account,

but still no luck installing any new apps or reinstalling old ones...

Any help would be greatly appreciated (or more tips on what else to try...).

PS: Apps load just fine in an emulator.
PS2: I can download and install apps from the store just fine [I found PixelMiner that way : )].
PS3: I do have a developer connection on and there is a valid IP shown on iOS app.

Solution

I got an answer from Morris on pebble forums. I was developing for SDK3, but still running older version of firmware on a pebble watch. After an update, deployment works again!

Original response:

You are building with the latest SDK but your watch has not the latest firmware.

You either have to upgrade your Pebble Classic to firmware V3.8.2 (see Upgrade to SDK3) or if you want to build for the old firmware you have to use SDK2 instead (see SDK2)